Kids' blocks brand (4)
I believe the answer is:
lego
'kids' blocks 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 "Toy building bricks" , "Child's building bricks" , "Building bricks for children" , "Toy with interlocking blocks" , "Building block toy" .)