Pa returns with a companion or fellow (4)
I believe the answer is:
chap
'fellow' is the definition.
(both can mean a man)
'pa returns with a companion' is the wordplay.
'returns' is a reversal indicator.
'with' is a charade indicator (letters next to each other).
'a companion' becomes 'ch' (Companion of Honour).
'pa' back-to-front is 'ap'.
'ap' after 'ch' is 'CHAP'.
'or' is the link.
(Other definitions for chap that I've seen before include "Become raw from cold - fellow" , "Man, sore patch" , "Split in skin" , "Sore; cheek; man" , "cove" .)