Stable establishment (4)
I believe the answer is:
firm
I believe this is a double definition.
'stable' is the first definition.
(similar in meaning)
'establishment' is the second definition.
(both can mean a business)
(Other definitions for firm that I've seen before include "Unflinching" , "Tight; company" , "Hard" , "A steady business enterprise? (4)" , "Steady sort of business organisation" .)