Gain pardon playing instrument (5,5)
I believe the answer is:
grand piano
'instrument' is the definition.
(I know that grand piano is a type of percussion instrument)
'gain pardon playing' is the wordplay.
'playing' is an anagram indicator.
'gain'+'pardon'='gainpardon'
'gainpardon' is an anagram of 'GRAND PIANO'.
(Other definitions for grand piano that I've seen before include "one getting tickled?" , "maker of notes?" , "Large instrument with horizontal strings" , "One's three-legged" , "Large stringed instrument" .)