Friend may be appearing during call (5)
I believe the answer is:
crony
'friend' is the definition.
(crony is a kind of friend)
'appearing during call' is the wordplay.
'appearing' becomes 'on' (e.g. on stage or on television).
'during' is an insertion indicator.
'call' becomes 'cry' ('cry' can be a synonym of 'call').
'on' placed into 'cry' is 'CRONY'.
'may be' is the link.
(Other definitions for crony that I've seen before include "Close companion" , "Close friend" , "Corny (anag.)" , "mate" , "Intimate companion" .)