Successful student receiving new piano (5)
I believe the answer is:
grand
'piano' is the definition.
(I know that grand is a type of piano)
'successful student receiving new' is the wordplay.
'successful student' becomes 'grad' (graduate).
'receiving' means one lot of letters goes inside another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'grad' placed around 'n' is 'GRAND'.
(Other definitions for grand that I've seen before include "Stately - splendid" , "great distinction" , "Comprehensive" , "principal" , "Imposing; PS1,000" .)