Green’s Dictionary of Slang

(Aus. prison) a warder who is bribed to smuggle items for the inmates.

1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xli 4/4: track: A person, usually a screw, who will take the odds of being sacked to make things a little easier for the prisoners by trafficking in goods in exchange for coin of the realm.
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Track. A prison warder who engages in trafficking with inmates.