Slidings played across the middle of piano (9)
I believe the answer is:
glissandi
'slidings played across the middle of piano' is the definition.
I can't judge whether this defines the answer.
'slidings played across the middle of piano' is the wordplay.
'played' indicates an anagram (letters playing around).
'across' indicates putting letters inside.
'the middle of' means to look at the middle letters.
The middle letter of 'piano' is 'a'.
'slidings' with letters rearranged gives 'glissndi'.
'glissndi' enclosing 'a' is 'GLISSANDI'.
Can you help me to learn more?
(Other definitions for glissandi that I've seen before include "Players may perform them" , "playing, while sliding up and down the passages" , "Series of rapidly ascending or descending musical notes" , "showing smooth actions" , "Musical terms" .)