Rat, for example (6)
I believe the answer is:
rodent
'rat for example' is the definition.
(rat is a kind of rodent)
This is the entire clue.
(Other definitions for rodent that I've seen before include "Vermin" , "Nibbler" , "Eg, capybara" , "Mouse or squirrel, say" , "Mouse, squirrel or rat" .)