Windows possibly get obscured or panes get misty (9,6)
I believe the answer is:
'windows possibly' is the definition.
'get obscured or panes get misty' is the wordplay.
'get obscured' is an anagram indicator.
'orpanesgetmisty' is an anagram of 'OPERATING SYSTEM'.
(Other definitions for operating system that I've seen before include "Software providing a computer's basic functions" , "Essential software" , "surgical procedure?" , "MO?" , "Essential computer facility" .)