Beach where nothing's under cover! (4)
I believe the answer is:
lido
'beach' is the definition.
(thesaurus)
'nothing's under cover' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'under' is a charade indicator (letters next to each other).
'cover' becomes 'lid' (lid is a kind of cover**).
'o' put after 'lid' is 'LIDO'.
'where' acts as a link.
(Other definitions for lido that I've seen before include "Swim here" , "Swimming and leisure area" , "Swimming bath" , "bathing-beach" , "Aquatic leisure centre" .)