ACROSS
1 It keeps one down-to-earth (1-5) G-FORCE
5 Secret session about withholding outdated currency (8)
9 Fe or Li’s period of radioactive decay (4-4)
10 Is a snotty person full of it? (6)
11 He discerns the state of the atmosphere by processing raw methane (10) WEATHERMAN
12 Garland on a princess (4) LEIA
13 Disgust expressed in ensuing merriment (8)
16 Talent can be hidden (6) LATENT
17 He’s let off from responsibility (6)
19 Disadvantage of guzzling a primarily straight alcoholic drink endlessly (not a gin cocktail) (8)
21 Man city (4)
22 Repressed criminal arrested, held in (10)
25 A bunch of characters in Java, perhaps (6)
26 Upset about a boy having primarily secret affairs (8)
27 Pilot is inwardly strict, in a cold-hearted manner (8)
28 English setter, with onset of Salmonellosis, is throwing up (6) EMESIS
DOWN
2 Animal trapped in iron structure (5)
3 Primarily, replace equipment functioning improperly, that is, overhaul (5)
4 Renowned specialist admitted me in, by accident (7)
5 Ocean (French ocean) drowns model ship (7)
6 With a change of direction, discussion becomes innovative (7)
7 Mushrooms expired, stuffed into cases improperly (9)
8 Warned against free education (9)
14 Mineral obtained from devastated blast area (9)
15 Lunatic raging about the congress (9)
18 Madly angered (7)
19 Criticise drama show (7)
20 Struggle with food served up raw, at first (7)
23 Problem child (5)
24 Dissatisfaction arising from lack of excitement over gaming console, so it’s said (5)