there may be a letter short in the clue:
16a Planting machine ate a lot of fuel (6) S?E??R looks like seeder??
there may be an extra letter in the clue:
1d Possibly oratorical types, mostly vexed about skill (7) ?I????S
4d Erased, under guidance, first of unread lines included (6) ???L?D
5d I take in couple shepherding doctor over vale, half heartedly (7) looks like arbiter with the "v" being extra (ale = bitter)