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