Hack food? (9)
I believe the answer is:
horsemeat
'hack food?' is the definition.
'horsemeat' can be an answer for 'food?' (horsemeat is a kind of food). I'm not certain of the 'hack' bit.
'hack food?' is the wordplay.
'hack' becomes 'horse' (I can't justify this - if you can you should give a lot more credence to this answer).
'food?' becomes 'meat' (meat is a kind of food).
'horse'+'meat'='HORSEMEAT'
Can you help me to learn more?
(Other definitions for horsemeat that I've seen before include "food fit for dogs" , "It's not served in most restaurants!" , "source of food adulteration?" .)