Stop eating firm meat (5)
I believe the answer is:
bacon
'meat' is the definition.
(bacon is a kind of meat)
'stop eating firm' is the wordplay.
'stop' becomes 'ban' (I've seen this before**).
'eating' is an insertion indicator.
'firm' becomes 'co' (a firm is a company).
'ban' placed around 'co' is 'BACON'.
(Other definitions for bacon that I've seen before include "English philosopher, d.1626 - Irish painter, d. 1992" , "Shakespeare's ghost, some say" , "Meat (brought home by a breadwinner?)" , "Francis -, twentieth century Ir. artist" , "Dried or smoked pig meat" .)