Passage of time managed by model (7)
I believe the answer is:
transit
'passage' is the definition.
('transit' can be a synonym of 'passage')
'time managed by model' is the wordplay.
'time' becomes 't'.
'managed' becomes 'ran' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'model' becomes 'sit' ('sit' can be a synonym of 'model'**).
't'+'ran'+'sit'='TRANSIT'
'of' is the link.
(Other definitions for transit that I've seen before include "In migration" , "Travel" , "Pass through; van" , "Start in for the process of being conveyed" , "Passage of a planet across the sun's disc" .)