Friend forced to accept retirement, primarily by firm (7)
I believe the answer is:
comrade
'friend' is the definition.
(I know that comrade is a type of friend)
'forced to accept retirement primarily by firm' is the wordplay.
'forced' becomes 'made' (both can mean coerced).
'to accept' means one lot of letters goes inside another.
'primarily' indicates taking the first letters.
'by' says to put letters next to each other.
'firm' becomes 'co' (a firm is a company).
The first letter of 'retirement' is 'r'.
'made' enclosing 'r' is 'mrade'.
'mrade' after 'co' is 'COMRADE'.
(Other definitions for comrade that I've seen before include "Fellow member of the armed forces" , "Colleague" , "Fellow left-winger" , "Fellow soldier" , "Fellow socialist or good friend" .)