Gallant chap in pain (7)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
paladin
'gallant' is the definition.
(thesaurus)
'chap in pain' is the wordplay.
'chap' becomes 'lad'.
'in' means one lot of letters goes inside another.
'lad' going inside 'pain' is 'PALADIN'.
(Other definitions for paladin that I've seen before include "One of the twelve peers at Charlemagne's court - heroic champion" , "paragon" , "Medieval champion" , "Heroic knight - aid plan (anag)" , "Knight errant; a peer of Charlemagne" .)