Rats, say (7)
I believe the answer is:
rodents
'rats say' is the definition.
(rat is a kind of rodent)
This is the entire clue.
(Other definitions for rodents that I've seen before include "Guinea pigs, hamsters etc" , "Animals that gnaw" , "Eg. rats" , "Eg, mice" , "Rats, mice, hamsters" .)