Intended one to pay for losing knight (6)
I believe the answer is:
fiance
'intended one' is the definition.
(one's intended is the person they're marrying)
'pay for losing knight' is the wordplay.
'pay for' becomes 'finance' (to finance something is to pay for it).
'losing' indicates named letters should be taken away.
'knight' becomes 'n' (chess abbreviation).
'finance' with 'n' taken out is 'FIANCE'.
'to' is the link.
(Other definitions for fiance that I've seen before include "The man she is going to marry" , "One engaged to marry" , "One who's engaged" , "One promised in marriage" , "Man engaged to marry" .)