Buzz off, small fly! Gone off (9)
I believe the answer is:
skedaddle
'buzz' is the definition.
The answer and definition can be both to do with motion as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'small fly gone off' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'fly' becomes 'ked' (type of parasitic fly).
'gone off' becomes 'addle' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
's'+'ked'+'addle'='SKEDADDLE'
'off' is the link.
Can you help me to learn more?
(Other definitions for skedaddle that I've seen before include "Escape" , "split" , "Quickly get out" , "run away" , "Bunk off quickly!" .)