Diana represented a female spirit (5)
I believe the answer is:
naiad
'a female spirit' is the definition.
'diana represented' is the wordplay.
'represented' indicates anagramming the letters.
'diana' is an anagram of 'NAIAD'.
(Other definitions for naiad that I've seen before include "watery spirit" , "Diana (anag.)" , "River nymph" , "Spring nymph" , "divine female figure" .)