Complain when a double rum is spilt (6)

I believe the answer is:

murmur

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'complain' is the definition.
(I know that murmur is a more specific form of the action complain)

'a double rum is spilt' is the wordplay.
'a double' becomes 'mur' (I am not sure about this - if you are sure you should believe this answer much more).
'is spilt' indicates an anagram.
'rum' is an anagram of 'mur'.
'mur'+'mur'='MURMUR'

'when' is the link.

Can you help me to learn more?

(Other definitions for murmur that I've seen before include "Soft voices (of discontent)" , "Undertone" , "Quietly spoken utterance; heart defect" , "Low background noise" , "Speak softly or indistinctly" .)

I've seen this clue in the Evening Standard.

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