ACROSS
1 Crazy? Ha ha, Kurt Cobain's 14 25 28 (13)
10 In a way that worries, changing from SW to N without changing directions (11)
11 Short section, 7x8x9 (3)
12 Does really well, exchanging large for small insurance complement (6)
13 Decoration is right in ship (8)
15 Wind down before opulence removing operation (10)
17 Outlaw folded-back collar (3)
19 Short official to sound hesitant, soft  (3)
20 Fire a nod, or otherwise preselect (10)
22 Second doctor partly alluding to return of the simple ... (8)
23 ... as outwardly tough mother shows health problem (6)
26 Boston's wet embargo – in all, the central element  (3)
27 Some land on tick?  Without $1000?  That's poetic (11)
28 Maniacal? Side 'A' proffers 1 (4,2,7)

DOWN
2 Score 99 with magic strokes (5)
3 14 of each futurist (thus Latin) lord (8)
4 Pin one in nothing (4)
5 Knife found in beast's heart? (3-7)
6 Oh to sound, to breathe! (6)
7 Rebuilt unmade tin plants' coats (9)
8 He, when very cold, gets this 9 about identity (13)
9 Ring Lynn, roll ball 12 (4-9)
14 Rebuilt on calf shed for which players switch ends (6,4)
16 Concerned with challenging sentences,  Apple tell a tale (having let Al off) (9)
18 Decorated female scholar pursues return of drudge (8)
21 Plumb a dairy shed: plumy fumes! (3,3)
24 She takes grave exception at her surrounds  (5)
25 Whip-cut (4)