Natasha's partner (5)
I believe the answer is:
boris
'natasha's partner' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for boris that I've seen before include "- Pasternak, Russian author (Doctor Zhivago)" , "-- Godunov; -- Johnson" , "Boy" , "Pasternak, perhaps" , "- Godunov, Russian tsar" .)