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 really see how this works, but
'superior' could be 'u' (U can mean upper-class, as in U and non-U speech) and 'u' is found within 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' is the 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?" .)