Boy crazy about girl (6)
I believe the answer is:
damsel
'girl' is the definition.
(I know that damsel is a type of maiden)
'boy crazy about' is the wordplay.
'boy' becomes 'les' (short for Leslie).
'crazy' becomes 'mad' (synonyms).
'about' is a reversal indicator.
'les'+'mad'='lesmad'
'lesmad' reversed gives 'DAMSEL'.
(Other definitions for damsel that I've seen before include "Maiden (poetic)" , "Young woman (often in distress)" , "Girl (literary)" , "Someone in distress?" , "Maid" .)