Woman's humour first to wilt (6)
I believe the answer is:
wither
'to wilt' is the definition.
(thesaurus)
'woman's humour first' is the wordplay.
'woman' becomes 'her' (her refers to a woman).
'humour' becomes 'wit' (synonyms).
'first' means one lot of letters go next to another.
'her' after 'wit' is 'WITHER'.
(Other definitions for wither that I've seen before include "Atrophy" , "Shrivel away" , "Turn dry and shrivelled" , "Dry up and perish" , "Dry up, decay" .)