Little pest (4)
(Other definitions for twerp that I've seen before include "Fool" , "Numpty" , "mug" , "Silly person" , "Nitwit" .)
'little pest' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gnat that I've seen before include "Small bloodsucker" , "small irritant" , "Woodland area" , "insect's" , "Small biting flying insect" .)
'little pest' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for urchin that I've seen before include "Small grubby boy or sea creature" , "Roguish child - especially one raggedly dressed" , "kid on street" , "Poor city child" , "Gamin" .)
(Other definitions for ant that I've seen before include "Termite" , "colonist" , "Dec's long-time partner" , "` `Go to the ... thou sluggard' '" , "Small busy insect" .)