Law about airgun debris (6)
I believe the answer is:
rubble
'debris' is the definition.
(I know that debris can be written as rubble)
'law about airgun' is the wordplay.
'law' becomes 'rule' (rule is a kind of law).
'about' means one lot of letters goes inside another.
'airgun' becomes 'bb' (I can't explain this - if you can you should give a lot more credence to this answer).
'rule' placed around 'bb' is 'RUBBLE'.
Can you help me to learn more?
(Other definitions for rubble that I've seen before include "Bits of broken stone, brick etc" , "Lose stones" , "Stone/brick waste" , "Mass of rough fragments of brick or stone" , "Debris left after building or demolition" .)