Custodian who does conscientious work? (9)
I believe the answer is:
caretaker
'custodian' is the definition.
(I know that caretaker is a type of custodian)
'does conscientious work?' is the wordplay.
I cannot really see how this works, but
'work?' could be 'take' (taking is a kind of working) and 'take' is found in the answer.
The remaining letters 'carer' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'who' is the link.
(Other definitions for caretaker that I've seen before include "exercising temporary control" , "Temporarily in charge" , "One looking after a building" , "Warden" , "Janitor" .)