Set off from college in time (8)
I believe the answer is:
detonate
'set off' is the definition.
('detonate' can be a synonym of 'set off')
'college in time' is the wordplay.
'college' becomes 'eton' (I've seen this before).
'in' means one lot of letters goes inside another.
'time' becomes 'date' (date is a kind of time**).
'eton' going into 'date' is 'DETONATE'.
'from' is the link.
(Other definitions for detonate that I've seen before include "Discharge" , "Start 15 [EXPLOSION]" , "Cause to explode" , "Set off explosive device" , "Trigger" .)