1 down. Emu’s tail (anag.). 8 letters.
2 down. Run-down. 6 letters.
3 down. Advise – edify. 6 letters.
4 down. Wild feline. 4 letters.
6 down. Cavy, for example. 6 letters and 3 letters.
7 down. Absurd. 9 letters.
12 down. Patrol vehicle. 5 letters and 3 letters.
14 down. Crotchety. 6 letters.
15 down. Fodder. 6 letters.
17 down. Discharge – receptacle. 4 letters.