Pioneer, he worked with originators of military project (11)
I believe the answer is:
oppenheimer
'pioneer he worked with originators of military project' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'pioneer he worked with originators of military project' is the wordplay.
'worked with' indicates anagramming the letters.
'originators of' suggests taking the first letters.
The initial letters of 'military project' is 'mp'.
'pioneer'+'he'='pioneerhe'
'pioneerhe' anagrammed with 'mp' makes 'OPPENHEIMER'.
(Other definitions for oppenheimer that I've seen before include "Atomic expert" , "Nuclear physicist" .)