Possibly license no noise (7)
I believe the answer is:
silence
'no noise' is the definition.
'possibly license' is the wordplay.
'possibly' indicates anagramming the letters.
'license' with letters rearranged gives 'SILENCE'.
(Other definitions for silence that I've seen before include "Quietude" , "Lack of sound" , "Quietness" , "Absence of racket" , "may be required in court" .)