Helper of Frankenstein (4)
I believe the answer is:
igor
'helper of frankenstein' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for igor that I've seen before include "Stravinsky's first name" , "-- Stravinsky, composer" , "Stravinsky, perhaps" , "Prince --, opera by Borodin" , "Prince of Russian opera" .)