Toy brick brand (4)
I believe the answer is:
lego
'toy brick brand' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lego that I've seen before include "construction kit" , "Building bricks for children" , "Toy building-bricks" , "Toy with interlocking blocks" , "Toy construction set" .)