Promise to marry female replacing each line in partnership (8)
I believe the answer is:
affiance
'promise to marry' is the definition.
(to affiance is to be someone's fiance or fiancee)
I don't understand the rest of the clue.
(Other definitions for affiance that I've seen before include "Bond" , "Betroth, become engaged" , "Betroth with face I fan" .)