Ariadne oddly selected assistant (4)
I believe the answer is:
aide
'assistant' is the definition.
(aide is a kind of assistant)
'ariadne oddly selected' is the wordplay.
'oddly selected' indicates alternate letters.
The alternate letters of 'ariadne' are 'AIDE'.
(Other definitions for aide that I've seen before include "Military officer acting as assistant" , "Somebody helping" , "Helper" , "Assistant to a more senior person" , "a help" .)