They simply adore leftovers! (6)
I believe the answer is:
lovers
'they simply' is the definition.
The definition suggests an adverb but the answer is not.
'adore leftovers' is the wordplay.
'adore' becomes 'love' (I've seen this in another clue).
'leftovers' becomes 'rs' (I can't justify this - if you can you should believe this answer much more).
'love'+'rs'='LOVERS'
Can you help me to learn more?
(Other definitions for lovers that I've seen before include "Fans" , "Romantic pair" , "Romeo and Juliet, perhaps" .)