Across:
1 Type of stress (ACCENT), in a manner of speaking (ACCENT),
4 Sounds like (= homophone indicator) Beany or Barney perhaps (Beany or Barney “Batchelors” peas and beans = one “batchelor” = “BACHELOR”) hasn’t got a regular mate (BACHELOR),
9 Dry type (CUR-E) admits taking head off (p) Irishman (‘Pat’ without ‘p’ = -AT-) (CURATE) assisting the minister (CURATE),
10 Menus are (menus are = USERNAME) wrong (= anagram indicator) for securing the online service (USERNAME),
12 Part of the golf course (ROUGH) proposal (PLAN) (ROUGH PLAN) is just a sketchy design (ROUGH PLAN),
13 Some remarkable aversion (some ‘remarkable aversion’ = LEAVE) to desert (desert/abandon = LEAVE),
14 Volte-face (CHANGE OF MIND) as a result of lobotomy perhaps (CHANGE OF MIND),
18 Taking the car (DRIVING) to the mountains (RANGE) (DRIVING RANGE) popular with the swingers (DRIVING RANGE),
21 Call up (EVOKE) first lady (EV-E) over fine (fine = okay = -OK-) (EVOKE),
22 If you’re involved in 15 down you’ll need this presumably (spend SEED MONEY in “gardening” perhaps) for financing start-ups (SEED MONEY),
24 Holds the discards (BIN LINER) for bait initially (‘bait’ initially = B-) in (-IN) big ship (LINER) (BIN LINER),
25 Individual (one = O’NE-) not in tip-top condition (-ILL) (O’NEILL) in Irish Dynasty (O’NEILL),
26 Final (LAST), final warning (final ‘warning’ = G-) for snaky type (-ASP) (LAST GASP) sounds like a touch of desperation (LAST GASP),
27 They put pressure on (GAUGES) to use gag (use gag = GAUGES) loosely (= anagram indicator).
Down:
1 The Joshua Tree (yucca) needs no introduction (y) (‘yucca’ without ‘y = ucca = ACCU-) – in retrospect (= reversal indicator), it’s suggestive (-RACY) (ACCURACY) of reliable hit (ACCURACY),
2 Crucial (crucial = CIRCULA-) play (= anagram indicator) with right (-R) (CIRCULAR) message for wider distribution (CIRCULAR),
3 Mark (mark = NOTCH) or Nick? (nick = NOTCH),
5 Not in school (ABSENT-) to look after (-MIND-) and feed half (‘feed’ half = -ED) (ABSENT-MINDED) the daydreamers (the ABSENT-MINDED),
6 It’s not easy (it’s HARD-) for those at the end of 24 across (end of “bin liner” = -LINER) (HARDLINER) opposing the peacemakers (HARDLINER),
7 A small (a small = LLAMAS) train (= anagram indicator) with pack animals (LLAMAS),
8 Created a stink (REEKED) for Weekender’s dropping of news (‘weekenders’ dropping of ‘news’ = eekder = REEKED),
11 What comes from the heart (BLOOD VESSELS) for family (BLOOD) going overseas (VESSELS) (BLOOD VESSELS),
15 Growing concern (GARDENING) for those involved in plot (GARDENING),
16 Organisation (UN-) is being wound up perhaps (-ENDING) (UNENDING) and it’s taking an age (UNENDING),
17 Keeps getting mileage out of (RECYCLES) crazy (= anagram indicator) secrecy (secrecy = RECYC-ES) about Labour leader (‘Labour’ leader = -L-) (RECYCLES),
19 Rosemary (HERB-) gets first (-A-) pound (pound = £ = -L) (HERBAL) of tea (HERBAL tea),
20 New (= anagram indicator) piston (piston = POINTS) required for electric motors (electric POINTS / plugs),
23 Grand (1,000 = M-) girl whatever way you look at her (Anna = -ANNA) (MANNA) is heaven-sent (MANNA).