Before end of day dining room is littered (5)
I believe the answer is:
messy
'is littered' is the definition.
(synonyms)
'before end of day dining room' is the wordplay.
'before' is a charade indicator (letters next to each other).
'end of' suggests the final letters.
'dining room' becomes 'mess' (mess is a kind of dining room).
The final letter of 'day' is 'y'.
'y' put after 'mess' is 'MESSY'.
(Other definitions for messy that I've seen before include "Untidy, dirty" , "Dirty and disorderly" , "Disorganised" .)