Strong and stable business (4)
I believe the answer is:
firm
This clue is a triple definition!
'strong' is the first definition.
('firm' can be a synonym of 'strong')
'and' is a link.
'stable' is the second definition.
('firm' can be similar in meaning to 'stable')
'business' is the third definition.
(firm is a kind of business)
(Other definitions for firm that I've seen before include "Determined" , "Steady sort of business organisation" , "Fixed" , "House" , "Solid; secure" .)