Gradual increase in sound sets red sconce quivering (9)
I believe the answer is:
crescendo
'gradual increase in sound' is the definition.
(I've seen this before)
'red sconce quivering' is the wordplay.
'quivering' indicates an anagram (letters shake or quiver into a new order).
'red'+'sconce'='redsconce'
'redsconce' is an anagram of 'CRESCENDO'.
'sets' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for crescendo that I've seen before include "Gradual increase in loudness, musically" , "Rising noise" , "climax" , "Becoming louder in soccer den" , "Gradually increasing in volume" .)