Youth in distress summons champion (7)
I believe the answer is:
paladin
'summons champion' is the definition.
'paladin' can be an answer for 'champion' (synonyms). I am unsure of the 'summons' bit.
'youth in distress' is the wordplay.
'youth' becomes 'lad' (lad means a young man).
'in' means one lot of letters goes inside another.
'distress' becomes 'pain' (I've seen this before).
'lad' going inside 'pain' is 'PALADIN'.
Can you help me to learn more?
(Other definitions for paladin that I've seen before include "Medieval champion" , "hero" , "Knight errant; a peer of Charlemagne" , "paragon" , "One of the twelve peers at Charlemagne's court - heroic champion" .)