Oppressive influence in copper business (7)
I believe the answer is:
incubus
'oppressive influence' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'in copper business' is the wordplay.
'copper' becomes 'Cu' (chemical symbol).
'business' becomes 'bus' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in'+'cu'+'bus'='INCUBUS'
Can you help me to learn more?
(Other definitions for incubus that I've seen before include "Nightmare - cub in us (anag)" , "Oppressive nightmare" , "Burdensome person or evil spirit visiting sleeper" , "Evil spirit visiting a sleeping person" , "Oppressive burden" .)