Pulse in early instrument (9)
I believe the answer is:
flageolet
This might be a double definition.
'pulse' is the first definition.
(I've seen this before)
'early instrument' is the second definition.
'flageolet' can be an answer for 'instrument' (I've seen this before). I'm not sure about the 'early' bit.
'in' is the link.
Can you help me to learn more?
(Other definitions for flageolet that I've seen before include "Instrument of the recorder family" , "Blow me" , "Pipe" , "instrument is played" , "musical instrument" .)