Company involved in growth is a nuisance (7)
I believe the answer is:
scourge
'a nuisance' is the definition.
(I have seen 'big nuisance' mean 'scourge' so perhaps 'nuisance' could also mean 'scourge')
'company involved in growth' is the wordplay.
'company' becomes 'co' (abbreviation).
'involved' means one lot of letters goes inside another.
'in growth' becomes 'surge' (I am not sure about this - if you are sure you should believe this answer much more).
'co' inserted within 'surge' is 'SCOURGE'.
'is' is the link.
Can you help me to learn more?
(Other definitions for scourge that I've seen before include "Curse; whip" , "Whip - bane" , "One causing great suffering; whip" , "Whip, flog" , "Person/thing causing great suffering; whip" .)