Mangy poodle’s internal pain (3)
I believe the answer is:
gyp
'pain' is the definition.
(I know that gyp is a type of hurt)
'mangy poodle's internal' is the wordplay.
'internal' indicates a hidden word.
'GYP' can be found hidden inside 'mangy poodles'.
(Other definitions for gyp that I've seen before include "Torture (sl.)" , "Cheat - discomfort" , "Swindle - pain - college servant" , "Pain, discomfort" , "college employee" .)