Pig food? It could be rigged (4)
I believe the answer is:
mast
'pig food?' is the definition.
'mast' can be an answer for 'food?' (mast is a kind of food). I'm not certain of the 'pig' bit.
'it could be rigged' is the wordplay.
I cannot really understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
The remaining letters 'mas' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for mast that I've seen before include "Pole aboard; fruit for pigs" , "Pole to support a sail" , "it rises on board a ship" , "Nuts for pigs" , "Tall pole from which flag is flown" .)