Unusually lad sings round sliding fingers over keyboard (9)
I believe the answer is:
glissando
'sliding fingers over keyboard' is the definition.
I can't judge whether this defines the answer.
'unusually lad sings round' is the wordplay.
'unusually' indicates an anagram.
'round' becomes 'o' (round can mean a round object).
'lad'+'sings'='ladsings'
'ladsings' anagrammed gives 'glissand'.
'glissand'+'o'='GLISSANDO'
Can you help me to learn more?
(Other definitions for glissando that I've seen before include "Effect produced by playing a series of notes very rapidly" , "Re-interpreting this musical direction" , "Sliding series of notes (mus.)" , "trombone slide, for example" , "Sliding effect in moving from one musical note to another" .)