Father left as an ally (3)
I believe the answer is:
'an ally' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's an association between them I don't understand?
'father left' is the wordplay.
'father' becomes 'pa' (pa is a kind of father**).
'left' becomes 'l' (common abbreviation).
'as' is the link.
Can you help me to learn more?
(Other definitions for pal that I've seen before include "Brother" , "Bud" , "Mate, informal friend" , "Close friend" , "Mate, buddy" .)