Centipede makes Hart droop, doctor! (9)
I believe the answer is:
arthropod
'centipede' is the definition.
(thesaurus)
'makes hart droop doctor' is the wordplay.
'makes' indicates an anagram.
'doctor' indicates an anagram.
'hart' with letters rearranged gives 'arth'.
'droop' is an anagram of 'ropod'.
'arth'+'ropod'='ARTHROPOD'
(Other definitions for arthropod that I've seen before include "Such as a crustacean or spider" , "worker, perhaps" , "One has external skeleton" , "Invertebrate" , "spider, for example" .)