Woman's gamble on husband (4)
I believe the answer is:
beth
'woman's' is the definition.
'gamble on husband' is the wordplay.
'gamble' becomes 'bet' (betting is a kind of gambling).
'on' says to put letters next to each other.
'husband' becomes 'h'.
'bet'+'h'='BETH'
(Other definitions for beth that I've seen before include "Girl" , "Hebrew letter; girl's name" , "letter to the Hebrews" , "Hebrew letter; a Little Woman" , "Concluding stanza" .)