The upper hand (7)
I believe the answer is:
foreman
'the upper hand' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'upper hand' is the wordplay.
'upper' becomes 'fore' (I can't justify this - if you can you should give a lot more credence to this answer).
'hand' becomes 'man' (both can mean a worker).
'fore'+'man'='FOREMAN'
Can you help me to learn more?
(Other definitions for foreman that I've seen before include "Male supervisor" , "Gaffer, overseer" , "Charge hand" , "Gaffer, boss" , "spokesman" .)