Polish seaside resort mentioned (8)
I believe the answer is:
brighten
'polish' is the definition.
(I've seen this before)
'seaside resort mentioned' is the wordplay.
'seaside resort' becomes 'Brighton'.
'mentioned' shows a homophone (sound like).
'brighton' is a homophone of 'BRIGHTEN'.
(Other definitions for brighten that I've seen before include "Liven up" , "Illuminate, cheer up" , "Polish" , "Berthing (anag.)" , "Cheer up; clear up" .)