Call bringing in working companion (5)
I believe the answer is:
crony
'companion' is the definition.
(I've seen this before)
'call bringing in working' is the wordplay.
'call' becomes 'cry' (as in a bird's call).
'bringing in' means one lot of letters goes inside another.
'working' becomes 'on' (e.g. a machine is working or on).
'cry' enclosing 'on' is 'CRONY'.
(Other definitions for crony that I've seen before include "Corny (anag.)" , "China" , "Intimate companion" , "Sidekick" , "Close companion" .)