Bustling mole with warm larva (8)
I believe the answer is:
mealworm
'larva' is the definition.
(I know that mealworm is a type of larva)
'bustling mole with warm' is the wordplay.
'bustling' indicates an anagram (letters bustle around).
'with' is a charade indicator (letters next to each other).
'mole' after 'warm' is 'warmmole'.
'warmmole' is an anagram of 'MEALWORM'.
(Other definitions for mealworm that I've seen before include "larva disliked by millers" , "Beetle larva" .)