Oafs had to open rubbish bags, dispersing balls (9)
I believe the answer is:
grapeshot
'balls' is the definition.
(ammunition consisting of metal balls)
'oafs had to open rubbish bags dispersing' is the wordplay.
'open' suggests taking the first letters (I've seen 'opens' mean this).
'rubbish' is an anagram indicator (a poor quality or rubbish spelling of the letters).
'bags' is an insertion indicator (bag can mean secures or steals).
'dispersing' becomes 'grapes' (I can't justify this - if you can you should believe this answer much more).
The initial letters of 'oafs had to' is 'oht'.
'oht' with letters rearranged gives 'hot'.
'hot' placed around 'grapes' is 'GRAPESHOT'.
Can you help me to learn more?
(Other definitions for grapeshot that I've seen before include "Charge for barrel" , "slugs?" , "Short page (anag) - ammunition for cannon" , "Great Balls of Fire" , "one could get peppered with it!" .)