Dispute right to enter complaint (5)
I believe the answer is:
argue
'dispute' is the definition.
(to argue something is to dispute or contest it)
'right to enter complaint' is the wordplay.
'right' becomes 'r' (common abbreviation).
'to enter' is an insertion indicator.
'complaint' becomes 'ague' (ague is a kind of health problem).
'r' inserted inside 'ague' is 'ARGUE'.
(Other definitions for argue that I've seen before include "contradict" , "Wrangle" , "Dispute, express angry words" , "Altercate" , "Quarrel, bicker" .)