Ceramic square (4)
I believe the answer is:
tile
'ceramic square' 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 "Thin slab of fired clay" , "Mah-jong piece" , "Scrabble piece" , "Roof slabs" , "Roofing slab" .)