Creature that burrows, destroying the marrow (9)
I believe the answer is:
earthworm
'creature that burrows' is the definition.
(creature that burrows underground)
'destroying the marrow' is the wordplay.
'destroying' indicates anagramming the letters.
'the'+'marrow'='themarrow'
'themarrow' is an anagram of 'EARTHWORM'.
(Other definitions for earthworm that I've seen before include "Soil dweller" , "Creature that burrows in soil" , "One burrows" , "What mole eats" , "that's throwing up on the lawn" .)