License absence of sound (7)

I believe the answer is:

silence

I'm a little stuck... Click here to teach me more about this clue!

'absence of sound' is the definition.
(I've seen this before)

'license' is the wordplay.
'license' can be anagrammed to 'SILENCE'.
However, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for silence that I've seen before include "Quiet" , "Quietude" , "Shut up!" , "What's left of burnt coal" , "may be required in court" .)

I've seen this clue in The Irish News.

Want a hint initially instead of a full solution? Install my app