Pause in bar after piano — nothing played fast (6)
I believe the answer is:
presto
'played fast' is the definition.
'presto' can be an answer for 'fast' (musical instruction). I'm not sure about the 'played' bit.
'pause in bar after piano nothing' is the wordplay.
'pause in bar' becomes 'rest' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'after' is a charade indicator (letters next to each other).
'piano' becomes 'p' (musical abbreviation).
'nothing' becomes 'O' (looks like zero - 0).
'rest' put after 'p' is 'prest'.
'prest'+'o'='PRESTO'
Can you help me to learn more?
(Other definitions for presto that I've seen before include "Hey ..., according to the magician" , "To be played quickly" , "Immediately" , "Poster (anag.)" , "quick to score" .)