Combine eg nitrate compounds (9)
I believe the answer is:
integrate
'combine' is the definition.
(integrating is a kind of combining)
'eg nitrate compounds' is the wordplay.
'compounds' indicates anagramming the letters.
'eg'+'nitrate'='egnitrate'
'egnitrate' with letters rearranged gives 'INTEGRATE'.
(Other definitions for integrate that I've seen before include "Join" , "Get together" , "Incorporate into the whole" , "unify" , "Mix" .)