Priest's moving spirit? (6)
I believe the answer is:
sprite
'spirit?' is the definition.
(thesaurus)
'priest's moving' is the wordplay.
'moving' indicates anagramming the letters (letters are moved around).
'priest' is an anagram of 'SPRITE'.
(Other definitions for sprite that I've seen before include "water pixie" , "Pet, sir, could be a goblin" , "Puck, say" , "Elf, fairy" , "Naiad" .)