Chivalrous champion of a chap in pain (7)
I believe the answer is:
paladin
'chivalrous champion' is the definition.
'paladin' can be an answer for 'champion' (synonyms). I'm not certain of the 'chivalrous' bit.
'a chap in pain' is the wordplay.
'a chap' becomes 'lad' ('lad' can be a synonym of 'chap').
'in' indicates putting letters inside.
'lad' going inside 'pain' is 'PALADIN'.
'of' is the link.
Can you help me to learn more?
(Other definitions for paladin that I've seen before include "Chivalrous knight" , "One of the twelve peers at Charlemagne's court - heroic champion" , "Knightly champion" , "Knight errant; a peer of Charlemagne" , "hero" .)