3 down
Whippersnapper
very
quietly
suppressing
single
sound
from
mouse
(9)
Whippersnapper very quietly suppressing single sound from mouse (9)
hints
0
checks
0
hints
The definition is at the beginning of the clue.
How the clue works
Whippersnapper is your definition, that cheeky young upstart. For the wordplay, "very quietly" in music terms gives you PP, and that suppresses (contains) "single", which is just I, giving you PIP — then you just tack on SQUEAK, the sound a mouse makes, to finish it off.