Restrict piano study first (5)
I believe the answer is:
cramp
'restrict' is the definition.
(I know that cramp is a more specific form of restrict)
'piano study first' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'study' becomes 'cram' (cramming is a kind of studying).
'first' is a charade indicator (letters next to each other).
'p' put after 'cram' is 'CRAMP'.
(Other definitions for cramp that I've seen before include "Involuntary and painful contraction of a muscle" , "Contract" , "writers may be familiar with" , "Painful muscle problem" , "Confine - muscular spasm" .)