Gunner takes off excited, scattering little balls (9)
I believe the answer is:
grapeshot
'scattering little balls' is the definition.
'grapeshot' can be an answer for 'balls' (ammunition consisting of metal balls). I am unsure of the 'scattering little' bit.
'gunner takes off excited' is the wordplay.
'gunner' becomes 'gr' (I can't explain this - if you can you should give a lot more credence to this answer).
'takes off' becomes 'apes'.
'excited' becomes 'hot' (I've seen this in another clue).
'gr'+'apes'+'hot'='GRAPESHOT'
Can you help me to learn more?
(Other definitions for grapeshot that I've seen before include "Short page (anag) - ammunition for cannon" , "Charge for barrel" , "Small projectiles fired from cannon" , "one could get peppered with it!" , "slugs?" .)