Twinge of constant inclination (5)
I believe the answer is:
cramp
'twinge' is the definition.
(thesaurus)
'constant inclination' is the wordplay.
'constant' becomes 'c' (mathematical abbreviation).
'inclination' becomes 'ramp' ().
'c'+'ramp'='CRAMP'
'of' acts as a link.
(Other definitions for cramp that I've seen before include "Involuntary muscular contraction" , "writers may be familiar with" , "Give too little space to" , "restraint" , "To restrict; a muscle pain" .)