Fashionable to rent in bay (5)
I believe the answer is:
inlet
'bay' is the definition.
(I've seen this before)
'fashionable to rent' is the wordplay.
'fashionable' becomes 'in' (similar in meaning).
'to rent' becomes 'let' ('let' can be a synonym of 'rent').
'in'+'let'='INLET'
'in' acts as a link.
(Other definitions for inlet that I've seen before include "Entry port" , "Bay or recess" , "bit of a lake here?" , "Opening through which liquid can flow" , "Coastal feature" .)