Eat like a rodent (4)
I believe the answer is:
gnaw
'eat like a rodent' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gnaw that I've seen before include "Bite and wear away" , "Attack with teeth" , "Prey on one's mind" , "Bite persistently, grind" , "Eat at" .)