Slide or jump, but not quietly (3)
I believe the answer is:
ski
'slide' is the definition.
(thesaurus)
'jump but not quietly' is the wordplay.
'jump' becomes 'skip' ('skip' can be a synonym of 'jump').
'but not' is a deletion indicator.
'quietly' becomes 'p' (p for piano and quiet).
'skip' with 'p' taken out is 'SKI'.
'or' acts as a link.
(Other definitions for ski that I've seen before include "Mountain runner" , "Descend fast" , "Snow blade" , "Walk on snow" , "Hit the slopes" .)