Nudge quietly with stick (4)
I believe the answer is:
prod
'nudge' is the definition.
(I know that nudge can be written as prod)
'quietly with stick' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'with' is a charade indicator (letters next to each other).
'stick' becomes 'rod' (I've seen this before).
'p'+'rod'='PROD'
(Other definitions for prod that I've seen before include "Poke (with a finger, etc)" , "Poke with stiff finger to urge" , "Poke - remind" , "Stimulus" , "Goad, stimulate into action" .)