Wife-to-be (5)
(Other definitions for bride that I've seen before include "new union member" , "presumably honeymoon for me?" , "She's just about to be married" , "Newlywed" , "Marriageable woman" .)
'wife-to-be' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for fiancee that I've seen before include "Girl engaged to marry" , "ringed girl" , "Promised" , "Intended" , "One engaged to be married" .)