Burrower disturbed the marrow (9)
I believe the answer is:
earthworm
'burrower' is the definition.
'disturbed the marrow' is the wordplay.
'disturbed' is an anagram indicator.
'the'+'marrow'='themarrow'
'themarrow' anagrammed gives 'EARTHWORM'.
(Other definitions for earthworm that I've seen before include "Creepy-crawly" , "One burrows" , "What mole eats" , "Creature that burrows in soil" , "Garden burrower" .)