Virgin goddess. Guardian angel? Not entirely (5)
I believe the answer is:
diana
'virgin goddess' is the definition.
(Roman goddess)
'guardian angel? not entirely' is the wordplay.
'not entirely' indicates the answer is hidden within the clue.
'DIANA' is hidden within 'guardian angel'.
(Other definitions for diana that I've seen before include "Roman godess of the hunt" , "MONKEY" , "Roman equivalent of Artemis" , "Roman huntress goddess" , "Roman goddess of the hunt, or tragic English princess" .)