A female's weak but fiery (6)
I believe the answer is:
aflame
'fiery' is the definition.
(thesaurus)
'a female's weak' is the wordplay.
'a female' becomes 'af' (I've seen this in other clues).
'weak' becomes 'lame' ('lame' can be similar in meaning to 'weak').
'af'+'lame'='AFLAME'
'but' acts as a link.
(Other definitions for aflame that I've seen before include "Ardent" , "Deeply aroused" , "Indicating excitement" , "On fire" , "Ablaze" .)