Joke framed by English chap promised in marriage (7)
I believe the answer is:
'promised in marriage' is the definition.
(I've seen this before)
'joke framed by english chap' is the wordplay.
'joke' becomes 'gag' (a gag is a joke or witticism).
'framed by' means one lot of letters goes inside another.
'english' becomes 'E' (abbreviation).
'chap' becomes 'ned' ().
'gag' put inside 'ened' is 'ENGAGED'.
(Other definitions for engaged that I've seen before include "Affianced" , "Preoccupied" , "Held" , "Busy, occupied" , "being committed to union" .)