Aunt set about making complaint (7)
I believe the answer is:
tetanus
'complaint' is the definition.
(tetanus is a kind of health problem)
'aunt set about' is the wordplay.
'about' indicates an anagram.
'aunt'+'set'='auntset'
'auntset' is an anagram of 'TETANUS'.
'making' is the link.
(Other definitions for tetanus that I've seen before include "Disease causing muscular spasms" , "Bacterial disease" , "Infection of the central nervous system" , "Attunes (anag) - muscular illness" , "Attunes to disease from dog-bite" .)