Contend that's not right, making complaint (4)
I believe the answer is:
ague
'complaint' is the definition.
(ague is a kind of disease)
'contend that's not right' is the wordplay.
'contend' becomes 'argue' ('argue' can be a synonym of 'contend').
'that's not' is a deletion indicator.
'right' becomes 'r' (common abbreviation).
'argue' with 'r' taken out is 'AGUE'.
'making' acts as a link.
(Other definitions for ague that I've seen before include "Malaria, for example" , "Fit of the shakes" , "Fit of shivering and shaking" , "Malarial fever or fit of shivering" , "nasty illness?" .)