Firm line (8)
I believe the answer is:
business
I believe this is a double definition.
'firm' is the first definition.
('business firm' can be a synonym of 'firm')
'line' is the second definition.
('business' can be a synonym of 'line')
(Other definitions for business that I've seen before include "Company U occupation" , "Firm" , "Baby" , "See 1" , "complicated problem" .)