Arden's delightful fourth has long words and phrases beautifully handled. I almost thought this was a themed one: parliaments (how about installing hammocks in parliament?), old official/leader,
1 Disgruntled chaplain, ignoring an Islamic leader (6) CALIPH (CHAPLAIN-AN)*
IS al-Baghdadi an example? Incidentally, the word Caliph contains the name 1 caliph starting from the 2nd letter, with a length of 3 letters, and is the name of the 4th caliph: Ali ! It is also found in the alternative spelling Khalifa
4 Can teach English to you in Germany by correspondence (8) EDUCABLE (E DU CABLE)
9 Nut going away afternoon (6) NOGGIN
10 Metal and Quartz form a grand structure (8) BASILICA (BA(for Barium) SILICA)
12 One can wear something white as an old official (8) PALATINE (A TIN in PALE)
13 Scorched design, perhaps (6) SINGED (DESIGN*)
Reminded me of an anecdote I had heard long back. A comedian (Groucho Marx?) had received a letter from a man requesting him to send a 'singed' photograph of his. Noting the spelling mistake, he gleefully took a photograph and using a cigarette lighter singed the edges and sent it. Promptly, another letter turned up: "Thank you for sending the signed photo, but I had asked for a singed one"
15 Jewish new year (4,8) ROSH HASHANAH (E/GK)
Remembered from Harold Robbins books, where I came across a host of new words like Bar Mitzvah, Yom Kippur, Yarmulke, etc.
18 Smart to acquire processed mineral, making things simple (12) STREAMLINING (MINERAL* in STING)
21 Order a sail with a native Indian (6) OJIBWA (O JIB W A)
22 Hurry to encode (8) SCRAMBLE (2)
24 Destitute and loveless, a characteristic picture (8) PORTRAIT (POOR-O TRAIT)
25 6 — true representation of righteousness (6) VIRTUE (VI TRUE*)
26 Breaking code in bet — it's related (8) ANECDOTE (CODE* in ANTE)
Ref. under 13a
27 Employed by a world body, absolutely new (6) UNUSED (UN USED)
1 Spin off participating in the central scheme (8) CONSPIRE (SPIN* in CORE)
2 Make it binding, say, among various allies (8) LEGALISE (EG in ALLIES*)
3 May be pertinent — what do you do in a wild party? (5,3,4,3) PAINT THE TOWN RED (PERTINENT WHAT DO)*
I wonder which colour the colour-blind paint the town with ...
5 Stretch upward (4) DRAW (WARD<)
I misread the first word as 'Sketch' and the clue still worked !
6 Dealt with antisocial — having an edge in making it illegal (15) CRIMINALISATION (RIM IN in ANTISOCIAL*)
7 Game for one newly married around midnight (6) BRIDGE (BRIDE around G)
This is the word that links two of Arden's favourites: the ship and the card game
8 Garfunkel and Simon — somewhat horny creatures (6) ELANDS (T)
Reverse order of the guys behind 'Silence of Sounds The' surprised me at first ! These guys were prescient - look, they predicted social media (ten thousand people, may be more - people talking without speaking), headphone/mobile usage that makes the user not to you when you talk directly with him/her (people hearing without listening), modern music (people writing songs that voices never share), computers/mobiles (the neon god that they had made) ...
On a different note, a lot of vehicle users in Bangalore are horny creatures too ...
11 Parliament seeks not to drop opposition leader after assembly (7) KNESSET (SEEKS NOT-O)*
14 Just the thing for retired swingers (7) HAMMOCK (CD)
16 Complaint when one perishes without help (8) DIABETES (DIES outside ABET)
17 Fit a tiny device initially in plant (8) AGUEWEED (AGUE WEE D)
19 Too much hype as it goes around a city (6) HOOPLA (HOOP LA)
20 May be Mary will go through it (6) PIERCE (2)
23 The thing that nourishes parliament (4) DIET (2)