7 across
Part
of
Arsenal’s
business
includes
ability
to
discern
pitch
(7)
Part of Arsenal’s business includes ability to discern pitch (7)
hints
0
checks
0
hints
The definition is at the beginning of the clue.
How the clue works
Part of Arsenal is the definition here, since an arsenal stores weapons and a firearm's one of them. For the wordplay, take FIRM (business) and stuff EAR (ability to discern pitch) inside it, splitting FIRM into FIR and M around EAR, which builds FIREARM.