Went off south with Guardian compilers' boss? (6)

I believe the answer is:

soured

'went off' is the definition.
(go off can mean to sour or decay)

'south with guardian compilers' boss?' is the wordplay.
'south' becomes 'S' (abbreviation).
'with' says to put letters next to each other.
'guardian compilers'' becomes 'our' (belonging to the setter and their colleagues).
'boss?' becomes 'ed' (short for editor - newspaper boss).
's'+'our'+'ed'='SOURED'

(Another definition for soured that I've seen is " Made bitter like milk".)

I've seen this clue in The Guardian.

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