Bachelor's first trendy place by the sea (8)
I believe the answer is:
brighton
'place by the sea' is the definition.
(UK city by the sea)
'bachelor's first trendy' is the wordplay.
'bachelor's first' becomes 'b' (1st letter of 'bachelor').
'trendy' becomes 'right on' (both can mean fashionably progressive).
'b'+'righton'='BRIGHTON'
(Other definitions for brighton that I've seen before include "Where the Prince Regent built his Pavilion" , "English resort with big thorn" , "South coast city combined with Hove" , "Sussex city (with Hove)" , "seaside location" .)