Former lover (3,5)
I believe the answer is:
old flame
'former lover' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for old flame that I've seen before include "Former lover" , "Former sweetheart" , "still 1 across [ALIGHT], it seems" , "Ex-lover - the fire still burns" , "Someone once loved" .)