Note player making a pile (7)
I believe the answer is:
reactor
'a pile' is the definition.
(I've seen this before)
'note player' is the wordplay.
'note' becomes 're'.
'player' becomes 'actor' ('actor' can be a synonym of 'player'**).
're'+'actor'='REACTOR'
'making' is the link.
(Other definitions for reactor that I've seen before include "Producer of nuclear energy" , "Nuclear power generator" , "Creator (anag.)" , "chemical substance!" , "nuclear facility" .)