Unusual of female to attend (7)
I believe the answer is:
offbeat
'unusual' is the definition.
(offbeat means unusual or whacky)
'of female to attend' is the wordplay.
'female' becomes 'f' (abbreviation).
'to attend' becomes 'beat' (to be at an event is to attend it).
'of'+'f'+'beat'='OFFBEAT'
(Other definitions for offbeat that I've seen before include "Wacky, eccentric" , "rather unorthodox" , "Odd, unconventional" , "Kooky" , "Strikingly unconventional" .)