Agree with boss, pointing up instrument (9)
I believe the answer is:
accordion
'instrument' is the definition.
(accordion is a kind of instrument)
'agree with boss' is the wordplay.
'agree with' becomes 'accord' (I've seen this before).
'boss' becomes 'ion' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'accord'+'ion'='ACCORDION'
'pointing up' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for accordion that I've seen before include "Cad I croon about a musical instrument" , "box-shaped musical instrument like melodeon" , "Squeeze box" , "Bellows-operated instrument" , "Agreement starts the musical instrument" .)