Block hiding other blocks (5)
I believe the answer is:
ingot
'block' is the definition.
(ingot is a kind of block)
'hiding other blocks' is the wordplay.
'blocks' indicates the answer is hidden within the clue (block can mean to contain or entrap).
'INGOT' is hidden in the letters of 'hiding other'.
(Other definitions for ingot that I've seen before include "Seize quickly; steal" , "Bar, often gold" , "Mass of cast metal" , "Brick-shaped lump of cast metal" , "Bar of bullion, for example" .)