Warning: a large branch by our cartoonist (5,4)

I believe the answer is:

alarm bell

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'warning' is the definition.

'a large branch by our cartoonist' is the wordplay.
'a large' becomes 'l'.
'branch' becomes 'arm' ('arm' can be a synonym of 'branch').
'by' is a charade indicator (letters next to each other).
'our' becomes 'a' (I can't justify this - if you can you should believe this answer much more).
'cartoonist' becomes 'bell' (Steve Bell - famous UK cartoonist).
'l'+'arm'='larm'
'larm' put after 'a' is 'alarm'.
'alarm'+'bell'='ALARM-BELL'

Can you help me to learn more?

(Other definitions for alarm bell that I've seen before include "Ring it to signal danger" , "It rings as a warning" , "Warning signal" , "Warning sound" , "Warning device" .)

I've seen this clue in The Guardian.

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