Father left as friend (3)
I believe the answer is:
pal
'friend' is the definition.
(pal is a kind of friend)
'father left' is the wordplay.
'father' becomes 'pa' (pa is a kind of father**).
'left' becomes 'l' (common abbreviation).
'pa'+'l'='PAL'
'as' acts as a link.
(Other definitions for pal that I've seen before include "Crony" , "Buddy, chum" , "Bud" , "China" , "Close friend" .)