Catholic inclination is a pain (5)
I believe the answer is:
cramp
'pain' is the definition.
(I have seen 'Muscular pain' mean 'cramp' so perhaps 'pain' could also mean 'cramp')
'catholic inclination' is the wordplay.
'catholic' becomes 'C' (abbreviation as in RC for Roman Catholic).
'inclination' becomes 'ramp' (an inclined surface).
'c'+'ramp'='CRAMP'
'is a' is the link.
(Other definitions for cramp that I've seen before include "Painful muscle problem" , "common among writers" , "development of vice" , "Severe muscular pain" , "To restrict; a muscle pain" .)