Forbid eating firm meat (5)
I believe the answer is:
bacon
'meat' is the definition.
(bacon is a kind of meat)
'forbid eating firm' is the wordplay.
'forbid' becomes 'ban' (banning is a kind of forbiding).
'eating' indicates putting letters inside.
'firm' becomes 'co' (a firm is a company).
'ban' placed around 'co' is 'BACON'.
(Other definitions for bacon that I've seen before include "Writer of essays" , "Meat - essayist - painter" , "Meat one can bring home" , "Francis --, Irish painter" , "Meat (that's brought home?)" .)