Withdrawing food with reduced fat is criminal (7)
I believe the answer is:
burglar
'is criminal' is the definition.
(I've seen this before)
'withdrawing food with reduced fat' is the wordplay.
'withdrawing' shows that the letters should be reversed in order.
'food' becomes 'grub' (grub can informally mean food).
'with' says to put letters next to each other.
'reduced' means to remove the last letter.
'fat' becomes 'lard' (lard is a kind of fat).
'grub' reversed gives 'burg'.
'lard' with its final letter removed is 'lar'.
'burg'+'lar'='BURGLAR'
(Other definitions for burglar that I've seen before include "Thief (entering building)" , "Thieving intruder" , "House thief" , "Building robber" , "One breaking in" .)