Foul now, unfit for consumption (2-3)

I believe the answer is:
in-off
'foul' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for in-off that I've seen before include "Billiards/snooker shot" , "Foul (snooker), scoring stroke (billiards)" , "Shot that's good at billiards and foul at snooker" , "Pocketing of a snooker ball via a deflection" , "Snooker hazard" .)
