It's painful parking after fitness centre closes early (3)
I believe the answer is:
gyp
'it's painful' is the definition.
(term for pain or irritation)
'parking after fitness centre closes early' is the wordplay.
'parking' becomes 'p'.
'after' is a charade indicator (letters next to each other).
'fitness centre' becomes 'gym' (I've seen this before).
'closes early' means to remove the last letter (I've seen 'closing early' mean this).
'gym' with its last letter taken off is 'gy'.
'p' after 'gy' is 'GYP'.
(Other definitions for gyp that I've seen before include "Swindle - pain - college servant" , "Cheat - discomfort" , "college employee" , "Torture (sl.)" , "Pain, discomfort" .)