Quiet work done by subordinate who makes plenty of sales (4,9)
I believe the answer is:
shop assistant
'subordinate who makes plenty of sales' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'quiet work' is the wordplay.
I cannot really see how this works, but
'quiet' could be 'sh' ('sh' is used to tell someone to be quiet) and 'sh' is found within the answer.
'work' could be 'assist' (assisting is a kind of working) and 'assist' is found in the answer.
This explanation may well be incorrect...
'done by' acts as a link.
Can you help me to learn more?
(Other definitions for shop assistant that I've seen before include "one employed in store" , "Give grass to aid one" , "who should be helping customers?" , "Salesperson" , "Worker in retail trade" .)