Crossword Genius

The partner dad left (3)

Ross

I believe the answer is:

'the partner' is the definition.
(I've seen this in other clues)

'dad left' is the wordplay.
'dad' becomes 'pa' (synonyms).
'left' becomes 'L' (common abbreviation).
'pa'+'l'='PAL'

(Other definitions for pal that I've seen before include "Buddy, chum", "Mate, informal friend", "Crony", "Friend (colloq.)", "China".)