Clothing manufacturer, increasingly friendly, inviting in corporation (9)
I believe the answer is:
costumier
'clothing manufacturer' is the definition.
(someone who makes costumes)
'increasingly friendly inviting in corporation' is the wordplay.
'increasingly friendly' becomes 'cosier' (more cosy).
'inviting in' indicates putting letters inside.
'corporation' becomes 'tum' ('corporation' can humorously mean belly fat).
'cosier' going around 'tum' is 'COSTUMIER'.
(Other definitions for costumier that I've seen before include "Tom Cruise (anag)" , "Supplier of stage clothes for actors" , "One making clothes" , "theatrical dresser" , "The person that dressed" .)