Green’s Dictionary of Slang

(N.Z.) a fight, a disturbance.

1960		N. Hilliard Maori Girl 257: There was a donny down at the Foresters tonight [...] Couple of them had this bloke down, one of them was beating him with a bottle.
1961		B. Crump Hang On a Minute, Mate 164: Some gate-crashing bushwhackers had picked on one of their blokes and it looked like a real donnie coming up.