One employing some house rules (4)
I believe the answer is:
user
'one employing' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'some house rules' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'USER' is hidden within 'house rules'.
Can you help me to learn more?
(Other definitions for user that I've seen before include "Drug-taker" , "With 1a [NEW] he'll need different login" , "Substance taker" , "Drug addict (informal)" , "Operator; exploiter" .)