Nevertheless, time is imagined (7)
I believe the answer is:
thought
'imagined' is the definition.
('think' can be a synonym of 'imagine')
'nevertheless time' is the wordplay.
'nevertheless' becomes 'though' (I've seen this before).
'time' becomes 't' (abbreviation).
'though'+'t'='THOUGHT'
'is' acts as a link.
(Other definitions for thought that I've seen before include "Idea coming to mind" , "Cogitated" , "just a trifle" , "Thinking process" , "Mental idea" .)