To sing badly must mean something (4)

I believe the answer is:

sign

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'must mean something' is the definition.
I can't tell whether this defines the answer.

'to sing badly' is the wordplay.
'badly' is an anagram indicator (letters in the wrong order).
'sing' anagrammed gives 'SIGN'.

Can you help me to learn more?

(Other definitions for sign that I've seen before include "Communicate silently" , "Public notice; portent" , "Signal, gesture" , "Public notice; Leo, say" , "Endorse" .)

I've seen this clue in the Evening Standard.

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