To sum up, offers blow over ecstasy at college (5)
I believe the answer is:
recap
'to sum up' is the definition.
(recapping is a kind of summing up)
'blow over ecstasy at college' is the wordplay.
'blow' becomes 'rap' (rap is a kind of blow**).
'over' is an insertion indicator.
'ecstasy' becomes 'e' (informal term for the drug).
'at' is a charade indicator (letters next to each other).
'college' becomes 'c'.
'e'+'c'='ec'
'rap' enclosing 'ec' is 'RECAP'.
'offers' is the link.
(Other definitions for recap that I've seen before include "Summary (abbr.)" , "Go back over the main points" , "Caper (anag)" , "Go over old ground" , "In brief, say it again" .)