Primate revealed by stream in part of India (7)
I believe the answer is:
gorilla
'primate' is the definition.
(I know that Gorilla is a type of primate)
'stream in part of india' is the wordplay.
'stream' becomes 'rill' (rill is a kind of stream).
'in' indicates putting letters inside.
'part of india' becomes 'goa' (Goa is in India).
'rill' inserted into 'goa' is 'GORILLA'.
'revealed by' is the link.
(Other definitions for gorilla that I've seen before include "Ape - aggressive muscleman" , "Large chest-beating ape" , "Largest living primate" , "African great ape" , "Chest-beating primate" .)