Some nice men taking building material (6)
I believe the answer is:
cement
'building material' is the definition.
(cement is a kind of building material)
'some nice men taking' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'CEMENT' is hidden within 'nice men taking'.
(Other definitions for cement that I've seen before include "Firmly establish" , "It hardens when water is added" , "material for bonding" , "Join firmly together" , "Ingredient of concrete" .)