Firm showing interest (7)
I believe the answer is:
concern
I believe this clue is a double definition.
'firm' is the first definition.
(both can mean an business)
'interest' is the second definition.
(I know that interest can be written as concern)
'showing' acts as a link.
(Other definitions for concern that I've seen before include "Feeling of anxiety or sympathy" , "Involve" , "Business - anxiety" , "Relate to; anxiety" , "Affect; solicitude" .)