Cunning, a desirable quality in pictures but not music (9)
I believe the answer is:
sharpness
I believe this is a double definition.
'cunning' is the first definition.
(thesaurus)
'a desirable quality in pictures but not music' is the second definition.
(photographs should be sharp)
(Other definitions for sharpness that I've seen before include "Clarity" , "Being quick to perceive" , "faulty intonation" , "Acuity; Severn port" .)