Crossword Genius

Don's left the ass a note! (3)

Ross

I believe the answer is:

key

'a note' is the definition.
(I know that key is a type of note)

'don's left the ass' is the wordplay.
'left' suggests deleting specific letters.
'the ass' becomes 'donkey' (donkey is a kind of ass).
'donkey' with 'don' removed is 'KEY'.

(Other definitions for key that I've seen before include "explanation" , "locker" , "Scale system for music" , "Lock undoer" , "Device for lock" .)

I've seen this clue in the Evening Standard.
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