Diners sadly are washed out (6)
I believe the answer is:
rinsed
'are washed out' is the definition.
(I've seen this in another clue)
'diners sadly' is the wordplay.
'sadly' indicates an anagram.
'diners' anagrammed gives 'RINSED'.
(Other definitions for rinsed that I've seen before include "Got rid of soap" , "Swilled" , "Washed out with fresh water" , "Washed out with clean water" .)