Element of skill on piano (4)
I believe the answer is:
part
'element' is the definition.
(a segment or piece)
'skill on piano' is the wordplay.
'skill' becomes 'art' (both can mean a talent).
'on' means one lot of letters go next to another.
'piano' becomes 'p' (musical abbreviation).
'art' after 'p' is 'PART'.
'of' acts as a link.
(Other definitions for part that I've seen before include "Fraction of the whole - separate" , "Region" , "Bit - leave" , "Some - theatrical role" , "Piece; divide" .)