Percussion instruments curtailed tempo with a lot of agitation (7)
I believe the answer is:
timpani
'percussion instruments' is the definition.
'curtailed tempo with a lot of agitation' is the wordplay.
'curtailed tempo with' becomes 'tim' (I can't justify this - if you can you should give a lot more credence to this answer).
'a lot of' means to remove the last letter (most of the word but not all of it).
'agitation' becomes 'panic' (I've seen this before).
'panic' with its last letter taken away is 'pani'.
'tim'+'pani'='TIMPANI'
(Other definitions for timpani that I've seen before include "Percussion section" , "part of kitchen?" , "Something making drumming noise" , "Mini tap on a large drum" , "Tina Pim has a set of kettle drums" .)