1 across. Composer, CPE or JS? 4 letters.
3 across. Atmospheric gas. 8 letters.
9 across. Russian playwright. 7 letters.
10 across. Defendable. 5 letters.
11 across. Succumb to giddiness. 5 letters.
12 across. Rile. 6 letters.
14 across. Wartime campaign slogan. 3 letters, 3 letters and 7 letters.
17 across. Butcher, at times. 6 letters.
19 across. Lot hammer? 5 letters.
22 across. Nonsense. 5 letters.
23 across. Pet. 7 letters.
24 across. Improve (as in the appearance of an image). 8 letters.
25 across. Twelve. 4 letters.