One can't believe it is an unfinished Schubert composition
I believe the answer is:
lie
'one can't believe it' is the definition.
I can't tell whether this defines the answer.
'an unfinished schubert composition' is the wordplay.
'an unfinished' means to remove the last letter.
'schubert composition' becomes 'lied' (I've seen this in another clue).
'lied' with its last letter removed is 'LIE'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for lie that I've seen before include "Porky" , "Tell porkies" , "Rest; deception" , "Fabrication" , "Disinformation" .)