Rhythmic monologue by an artist at the piano (3)
I believe the answer is:
rap
'rhythmic monologue' is the definition.
(I've seen this before)
'an artist at the piano' is the wordplay.
'an artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'at' is a charade indicator (letters next to each other).
'the piano' becomes 'p' (musical abbreviation).
'ra'+'p'='RAP'
'by' acts as a link.
(Other definitions for rap that I've seen before include "Music; charge; strike" , "Knock, tap" , "Form of music with spoken lyrics" , "talking during musical performance" , "Rhyming monologue recited to rock music below par" .)