Speed of piano expert? (4)
I believe the answer is:
pace
'speed' is the definition.
(pace is a kind of speed)
'piano expert?' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'expert?' becomes 'ace' (ace can informally mean very good).
'p'+'ace'='PACE'
'of' acts as a link.
(Other definitions for pace that I've seen before include "Stride" , "a certain distance" , "With the leave of; speed" , "Lick" , "Step or tempo" .)