Leather firm is welcoming radio operator (7)
I believe the answer is:
chamois
'leather' is the definition.
(chamois is a kind of leather)
'firm is welcoming radio operator' is the wordplay.
'firm' becomes 'co' (abbreviation for company).
'welcoming' means one lot of letters goes inside another (in sense of 'inviting in').
'radio operator' becomes 'ham' (as in ham radio).
'co'+'is'='cois'
'cois' enclosing 'ham' is 'CHAMOIS'.
(Other definitions for chamois that I've seen before include "Window cleaner" , "wild animals" , "Mountain antelope - soft leather" , "Mountain-dwelling antelope" , "Hide" .)