Gnawing mammals (7)
I believe the answer is:
rodents
'gnawing mammals' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rodents that I've seen before include "Eg, mice" , "Mice, squirrels etc" , "Animals that gnaw" , "Rats, mice, hamsters" , "Rats and mice, say" .)