Pope concealing weapon smoothly (6)
I believe the answer is:
legato
'smoothly' is the definition.
(I've seen this in another clue)
'pope concealing weapon' is the wordplay.
'pope' becomes 'leo' (papal name of several popes).
'concealing' indicates putting letters inside.
'weapon' becomes 'gat' (gat is a kind of weapon).
'leo' going around 'gat' is 'LEGATO'.
(Other definitions for legato that I've seen before include "Got ale (anag.)" , "Smoothly (mus.)" , "play on without pause" , "(Music) without breaks between notes" , "Smoothly, musically speaking" .)