Dined in college, by the sound of it (5)
I believe the answer is:
eaten
'dined' is the definition.
(having had a meal)
'college by the sound of it' is the wordplay.
'college' becomes 'eton' (Eton College, English private school).
'by the sound of it' shows a homophone (sound like).
'eton' is a homophone of 'EATEN'.
'in' is the link.
(Other definitions for eaten that I've seen before include "dinners should be" , "Crammed" , "worried" , "Scoffed" , "What's taken in" .)