Watch and see how long the music takes (9)
I believe the answer is:
timepiece
'watch' is the definition.
(I've seen this before)
'see how long the music takes' is the wordplay.
I cannot really understand how this works, but
'see' could be 'c' (the word for the letter, according to Chambers) and 'c' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'music' could be 'me' and 'me' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'and' acts as a link.
Can you help me to learn more?
(Other definitions for timepiece that I've seen before include "Clock, for example" , "Chronometer" , "Maybe hunter" , "alarm, perhaps" , "Watch, say" .)