Din in to the groom that it's a mess (6,4)
I believe the answer is:
dining room
'it's a mess' is the definition.
(I've seen this before)
'din in to the groom' is the wordplay.
'to the groom' becomes 'groom'.
'din'+'in'+'groom'='DINING-ROOM'
'that' acts as a link.
(Other definitions for dining room that I've seen before include "place for courses?" , "refectory" , "Where meals are eaten" , "eating-place" , "mess" .)