Doctor getting to grips with youth leader’s severe pain (3)
I believe the answer is:
gyp
'severe pain' is the definition.
'doctor getting to grips with youth leader's' is the wordplay.
'doctor' becomes 'gp' (general practitioner).
'getting to grips with' indicates putting letters inside.
'youth leader' becomes 'y' (I've seen this in other clues).
'gp' going around 'y' is 'GYP'.
(Other definitions for gyp that I've seen before include "Swindle - pain - college servant" , "Torture (sl.)" , "Pain, discomfort" , "Pain (slang)" , "Cheat - discomfort" .)