Tremble when passing notes around, short ones (15)
I believe the answer is:
Here is my best explanation:
'short ones' is the definition.
Although both the answer and definition are plural nouns, I don't see how they can define each other.
'tremble when passing notes' is the wordplay.
I cannot quite see how this works, but
'tremble' could be 'quaver' (I've seen this before) and 'quaver' is found within the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is found in the answer.
'notes' could be 'mi' and 'mi' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'around' acts as a link.