At first some take up commercial construction of building material (6)
I believe the answer is:
stucco
'building material' is the definition.
(I've seen this in another clue)
'at first some take up commercial construction of' is the wordplay.
'at first' suggests taking the first letters.
The first letters of 'some take up commercial construction of' is 'STUCCO'.
(Other definitions for stucco that I've seen before include "Kind of plaster used for wall decoration" , "Fine plaster used in cornices, mouldings" , "Coating material" , "Decorative external plaster" , "Plaster for coating or moulding" .)