Barbie's partner (3)
I believe the answer is:
ken
'barbie's partner' is the definition.
(boyfriend of the Barbie doll)
This is the entire clue.
(Other definitions for ken that I've seen before include "Understanding - boy's name" , "Know; man's name" , "One's range of knowledge" , "Awareness" , "Identify; -- Livingstone" .)