All the broken stone that goes into concrete (9)
I believe the answer is:
aggregate
'all the broken stone that goes into concrete' is the definition.
'aggregate' can be an answer for 'all' (thesaurus). I am unsure of the rest of the definition.
'all the broken stone' is the wordplay.
'all' becomes 'greg' (I can't justify this - if you can you should give a lot more credence to this answer).
'the broken' indicates putting letters inside (inserted letters break into others).
'stone' becomes 'agate' (agate is a type of stone).
'greg' going inside 'agate' is 'AGGREGATE'.
Can you help me to learn more?
(Other definitions for aggregate that I've seen before include "Combined or total amount" , "Sum of many heterogenous things taken together" , "Solid rock" , "Combine into a whole" , "Get garage to do sum" .)