Orchestra pits played extremely high (13)
I believe the answer is:
stratospheric
'extremely high' is the definition.
(the stratosphere is part of the atmosphere)
'orchestra pits played' is the wordplay.
'played' indicates anagramming the letters (letters playing around).
'orchestra'+'pits'='orchestrapits'
'orchestrapits' is an anagram of 'STRATOSPHERIC'.
(Other definitions for stratospheric that I've seen before include "Belonging to the upper air" , "Very high" , "Sky-high (informal)" .)