His visitors may take a dim view of him at first (7)
I believe the answer is:
oculist
'his visitors may take a dim view' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'of him at first' is the wordplay.
'of' becomes 'o''.
'him at' becomes 'cul' (I can't justify this - if you can you should believe this answer much more).
'first' becomes 'ist' (ist resembles cst).
'o'+'cul'+'ist'='OCULIST'
Can you help me to learn more?
(Other definitions for oculist that I've seen before include "Specialist in treatment of the eyes" , "Person of vision" , "Old-fashioned eye doctor" , "Specialist in defects and diseases of the eye" , "Optician" .)