Can’t parse final two.
25a Works jockeys without staff at first (7)
O-u-r-s
Oeuvres?
28a Discourage three consecutive semitones (7)
D-f-a-e
Deflate?
I can see that d, e-flat and e are musical notes but why semitones when they could be tones, quavers or any other sort of note?