Be slow to leave (6)
I believe the answer is:
linger
'be slow to leave' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for linger that I've seen before include "'Loiter, delay leaving (6)'" , "Be slow to go" , "Delay departure" , "Dally, stay on" , "Leave slowly and hesitantly" .)