Consider tailless rodent (3)
I believe the answer is:
rat
'rodent' is the definition.
(rat is a kind of rodent)
'consider tailless' is the wordplay.
'consider' becomes 'rate' (I've seen this before).
'tailless' means to remove the last letter.
'rate' with its last letter taken away is 'RAT'.
(Other definitions for rat that I've seen before include "one who deserts the sinking ship?" , "person doing shopping" , "Sewer rodent" , "Abandon" , "Unpopular rodent" .)