Father left friend (3)
I believe the answer is:
pal
'friend' is the definition.
(pal can mean a friend)
'father left' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'left' becomes 'l' (common abbreviation).
'pa'+'l'='PAL'
(Other definitions for pal that I've seen before include "Brother" , "China" , "Bud" , "Mate, informal friend" , "Buddy, chum" .)