Established company (4)
I believe the answer is:
firm
I believe this clue is a double definition.
'established' is the first definition.
('firm' can be a synonym of 'established')
'company' is the second definition.
(thesaurus)
(Other definitions for firm that I've seen before include "Business company" , "Solid; secure" , "Steady and unyielding, like business organisation" , "Fixed" , "Hard" .)