Using sound, very delicate note dropped (5)
I believe the answer is:
sonic
'dropped' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I can't see?
'using sound very delicate note' is the wordplay.
I cannot quite understand how this works, but
'using' could be 'on' (someone using drugs is 'on' them) and 'on' is found within the answer.
'note' could be 'si' (I've seen this in other clues) and 'si' is found in the remaining letters.
A single letter 'c' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sonic that I've seen before include "Boom of jet aircraft" , "Like mine, possibly" , "Using waves" , "Employing sound" , "Hedgehog" .)