Drums start, I'm panicking within (7)
I believe the answer is:
timpani
'drums' is the definition.
(type of drums)
'start i'm panicking within' is the wordplay.
'within' indicates a hidden word.
'TIMPANI' can be found hidden inside 'start im panicking'.
(Other definitions for timpani that I've seen before include "orchestra members" , "Features of kitchen" , "Percussion section" , "Main pit (anag) - drums" , "PM, I ain't (anag.)" .)