Employer of a superior, fault free service (4)
I believe the answer is:
user
'employer' is the definition.
(someone who employs or uses something)
'superior fault free service' is the wordplay.
I cannot quite understand how this works, but
'superior' could be 'u' (U can mean upper-class, as in U and non-U speech) and 'u' is present in the answer.
The remaining letters 'ser' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of a' acts as a link.
Can you help me to learn more?
(Other definitions for user that I've seen before include "Utiliser" , "Drug taker" , "Patron" , "Maybe one needing pot" , "Tech support caller?" .)