Complaint from a visitor, not good person (4)
I believe the answer is:
ague
'complaint' is the definition.
(ague is a kind of disease)
'a visitor not good person' is the wordplay.
'visitor' becomes 'guest' (guest is a kind of visitor).
'not' indicates named letters should be taken away.
'good person' becomes 'st' (saint).
'guest' with 'st' taken away is 'gue'.
'a'+'gue'='AGUE'
'from' acts as a link.
(Other definitions for ague that I've seen before include "Burning fever" , "Feverish illness" , "Old word for fever" , "attack" , "Fever (archaic)" .)