Mahjong piece (4)
I believe the answer is:
tile
'mahjong piece' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tile that I've seen before include "Scrabble piece" , "Roofing or flooring item" , "Piece on roof" , "Thin rectangular slab to cover surfaces" , "Oblong piece of glazed clay for bathroom wall" .)