Prohibition restricts firm producing meat (5)
I believe the answer is:
bacon
'meat' is the definition.
(bacon is a kind of meat)
'prohibition restricts firm' is the wordplay.
'prohibition' becomes 'ban' (ban is a kind of prohibition).
'restricts' is an insertion indicator.
'firm' becomes 'co' (a firm is a company).
'ban' going around 'co' is 'BACON'.
'producing' acts as a link.
(Other definitions for bacon that I've seen before include "Author" , "Salted pig-meat" , "Old scientist" , "Shakespeare's ghost, some say" , "Francis or Roger?" .)