He makes a practice of seeing complaints (7)
I believe the answer is:
oculist
'he makes a practice of seeing complaints' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for oculist that I've seen before include "Former name for an ophthalmologist" , "Person of vision" , "Treater of eyes" , "Specialist in treatment of the eyes" , "Visionary healer" .)