A copper climbing around top of tower to aim loaded weapon (9)
I believe the answer is:
automatic
'weapon' is the definition.
(automatic firearm)
'a copper climbing around top of tower to aim loaded' is the wordplay.
'a copper' becomes 'cua' (I can't explain this - if you can you should believe this answer much more).
'climbing' says the letters should be written in reverse (in a down clue, letters climb up).
'around' indicates putting letters inside.
'top of' indicates taking the first letters.
'loaded' indicates an anagram (loaded can mean drunk).
The first letter of 'tower' is 't'.
'cua' written backwards gives 'auc'.
't'+'to'+'aim'='ttoaim'
'ttoaim' anagrammed gives 'tomati'.
'auc' placed around 'tomati' is 'AUTOMATIC'.
Can you help me to learn more?
(Other definitions for automatic that I've seen before include "Functioning without human intervention" , "Working by itself" , "washing-machine?" , "Unmanned" , "Done without conscious thought" .)