Puritan quietly getting the gear (4)
I believe the answer is:
prig
'puritan' is the definition.
(thesaurus)
'quietly getting the gear' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'getting' is a charade indicator (letters next to each other).
'the gear' becomes 'rig' (rig is a kind of gear**).
'p'+'rig'='PRIG'
(Other definitions for prig that I've seen before include "Puritanical or arrogant and annoying person" , "Sanctimonious person" , "Goody-goody" , "Smugly self-righteous person" , "Smug type" .)