Show range on piano (5)
I believe the answer is:
prove
'show' is the definition.
(synonyms)
'range on piano' is the wordplay.
'range' becomes 'rove' (synonyms).
'on' says to put letters next to each other.
'piano' becomes 'p' (musical abbreviation).
'rove' put after 'p' is 'PROVE'.
(Other definitions for prove that I've seen before include "Demonstrate beyond doubt" , "13 [SHOW]" , "Ascertain" , "Demonstrate to be true" , "Demonstrate (truth)" .)