Instrument puts monarch on tape (8)
I believe the answer is:
recorder
'instrument' is the definition.
(I know that recorder is a type of pipe)
'puts monarch on tape' is the wordplay.
'puts monarch' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' is a charade indicator (letters next to each other).
'tape' becomes 'record' (synonyms).
'er' put after 'record' is 'RECORDER'.
Can you help me to learn more?
(Other definitions for recorder that I've seen before include "A kind of flute or note-taker" , "Fipple-flute" , "Wind instrument - historian, perhaps" , "Wind instrument much used in schools" , "found on the bench" .)