Very successful young person with sub-species? (10)
I believe the answer is:
wunderkind
'very successful young person' is the definition.
'with sub-species?' is the wordplay.
'with' becomes 'w' (abbreviation).
'sub' becomes 'under' (I've seen this before).
'species?' becomes 'kind' (species is a kind of kind).
'w'+'under'+'kind'='WUNDERKIND'
(Other definitions for wunderkind that I've seen before include "One having early success" , "Perhaps Mozart" , "Clever young person" , "Child prodigy" , "Extraordinary issue" .)