Inflexible in business (4)
I believe the answer is:
firm
I believe this clue is a double definition.
'inflexible' is the first definition.
(thesaurus)
'business' is the second definition.
(I know that firm is a type of business)
'in' acts as a link.
(Other definitions for firm that I've seen before include "Fixed" , "unlikely to collapse" , "Resistant to pressure" , "Unflinching" , "Strong - business" .)