Where Jezebel is found welcoming a husband's vow (4)
I believe the answer is:
oath
'vow' is the definition.
('oath' can be a synonym of 'vow')
'where jezebel is found welcoming a husband's' is the wordplay.
'where jezebel is found' becomes 'ot' (Old Testament).
'welcoming' indicates putting letters inside (in sense of 'inviting in').
'husband' becomes 'h'.
'ot' going around 'a' is 'oat'.
'oat'+'h'='OATH'
(Other definitions for oath that I've seen before include "Tedious task" , "gadzooks!" , "Swear word" , "'Profane, or solemn expression (4)'" , "One sworn" .)