Crusade opponent succeeded by a young man at home (7)
I believe the answer is:
saladin
'crusade opponent' is the definition.
(I've seen this before)
'succeeded by a young man at home' is the wordplay.
'succeeded' becomes 's' (genealogical abbreviation).
'by' is a charade indicator (letters next to each other).
'young man' becomes 'lad' (lad can mean a boy or young man).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
's'+'a'+'lad'+'in'='SALADIN'
(Other definitions for saladin that I've seen before include "Richard the Lionheart's enemy" , "Crusade warrior" , "Richard's enemy" , "Saracen leader" , "Crusade foe of Richard I" .)