Hard business (4)
I believe the answer is:
firm
I believe this clue is a double definition.
'hard' is the first definition.
('firm' can be similar in meaning to 'hard')
'business' is the second definition.
(firm is a kind of business)
(Other definitions for firm that I've seen before include "Resolute; company" , "Solid - business" , "Company - solid" , "Not soft or yielding to pressure" , "decided" .)