Call friend over (3)
I believe the answer is:
dub
'call' is the definition.
(I've seen this before)
'friend over' is the wordplay.
'friend' becomes 'bud' (shortly for buddy).
'over' says the letters should be written backwards.
'bud' written backwards gives 'DUB'.
(Other definitions for dub that I've seen before include "Copy to tape or disc" , "type of music" , "Ennoble" , "Confer a title on" , "Give nickname, knighthood, to" .)