Find fault with John setting up lift mechanism (3,4)
I believe the answer is:
car pool
'lift mechanism' is the definition.
The definition suggests a singular noun which matches the answer.
'find fault with john setting up' is the wordplay.
'find fault' becomes 'carp' (I've seen this before).
'with' means one lot of letters go next to another.
'john' becomes 'loo' (both can mean a toilet).
'setting up' says the letters should be written backwards.
'loo' written backwards gives 'ool'.
'carp'+'ool'='CAR-POOL'
Can you help me to learn more?
(Other definitions for car pool that I've seen before include "Passenger vehicles owned by a company for use by employees" , "arrangement of lifts?" , "Vehicles for shared use" .)