Play an essential part but not out there (6)
I believe the answer is:
inhere
'play an essential part but' is the definition.
I can't tell whether this definition defines the answer.
'not out there' is the wordplay.
'not out' becomes 'in' ('in' is the opposite to 'out').
'there' becomes 'here' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in'+'here'='INHERE'
Can you help me to learn more?
(Other definitions for inhere that I've seen before include "Belong essentially" , "Stick" , "Be a necessary element - at this place" , "Belong, live" , "Exist essentially" .)