Poor Darth turned into - a spider? (9)
I believe the answer is:
arthropod
'a spider?' is the definition.
(spider is a kind of arthropod)
'poor darth turned' is the wordplay.
'turned' indicates an anagram.
'poor'+'darth'='poordarth'
'poordarth' with letters rearranged gives 'ARTHROPOD'.
'into' is the link.
(Other definitions for arthropod that I've seen before include "Creature such as insect or crustacean" , "worker, perhaps" , "One has external skeleton" , "Invertebrate" , "Such as a crustacean or spider" .)