Cut off something that may be wagging (7)
I believe the answer is:
curtail
'cut off' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for curtail that I've seen before include "Dock" , "make shorter" , "Reduce in extent" , "Abbreviate" , "Cut short (an activity)" .)