Is no longer (3)
I believe the answer is:
was
'is no longer' is the definition.
(eg if someone 'was' sad, they're no longer sad)
This is all the clue.
(Other definitions for was that I've seen before include "Used to be" , "'Is, in the past (3)'" , "Is no longer" , "Did live" , "(I/he/she/it) existed" .)