Primate revealed by stream in part of India (7)
I believe the answer is:
gorilla
'primate' is the definition.
(gorilla is a kind of primate)
'stream in part of india' is the wordplay.
'stream' becomes 'rill' (rill is a kind of stream).
'in' means one lot of letters goes inside another.
'part of india' becomes 'goa' (Goa is in India).
'rill' going within 'goa' is 'GORILLA'.
'revealed by' acts as a 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" .)