Collect material for concrete (9)
I believe the answer is:
aggregate
'collect' is the definition.
(thesaurus)
'material for concrete' is the wordplay.
I cannot quite understand how this works, but
'material' could be 'ag' (Ag is an example) and 'ag' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for aggregate that I've seen before include "Total of several separate elements" , "Collective total - a great egg (anag)" , "Sum total" , "All - broken stone put in cement" , "Collected" .)