Big weapons British note missing from Welsh town (9)
I believe the answer is:
artillery
'big weapons' is the definition.
(I've seen this in another clue)
'british note missing from welsh town' is the wordplay.
I cannot quite understand how this works, but
'note' could be 'ti' (musical note, as in do re mi so fa la ti do) and 'ti' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for artillery that I've seen before include "Large guns for army in land war" , "Large pieces" , "Gunners" , "Ordnance" , "Large-calibre guns" .)