Team-mate in company joins liberal association (9)
I believe the answer is:
colleague
'team-mate' is the definition.
(I know that team-mate can be written as colleague)
'company joins liberal association' is the wordplay.
'company' becomes 'co' (abbreviation).
'joins' says to put letters next to each other.
'liberal' becomes 'l' (abbreviation).
'association' becomes 'league' (league is a kind of association).
'co'+'l'+'league'='COLLEAGUE'
'in' acts as a link.
(Other definitions for colleague that I've seen before include "Fellow worker" , "fellow member of staff" , "China, perhaps" , "Person with whom one works" , "Business co-worker" .)