Doctor entering dark place where young play (12)
I believe the answer is:
kindergarten
'place where young play' is the definition.
(children go to kindergarten)
'doctor entering dark' is the wordplay.
'doctor' indicates anagramming the letters.
'entering'+'dark'='enteringdark'
'enteringdark' is an anagram of 'KINDERGARTEN'.
(Other definitions for kindergarten that I've seen before include "Infant school" , "Pre-primary school class" , "Children's school" , "Playgroup" , "Pre-school class" .)