College with fashionable folk by the sea in Brittany (6)
I believe the answer is:
merton
'college' is the definition.
(Oxford University college)
'fashionable folk by the sea in brittany' is the wordplay.
'fashionable folk' becomes 'ton' ('the ton' can mean fashionable society).
'by' says to put letters next to each other.
'the sea in brittany' becomes 'mer' (French for 'sea').
'ton' after 'mer' is 'MERTON'.
'with' is the link.
(Other definitions for merton that I've seen before include "Comic" , "Oxford college: London borough" .)