They stop the traffic when noted ship has sailed off (8,6)

I believe the answer is:

lollipop ladies

'they stop the traffic' is the definition.

'noted ship has sailed off' is the wordplay.
'noted ship' becomes 'lollipop'.
'has' says to put letters next to each other.
'off' is an anagram indicator.
'sailed' with letters rearranged gives 'ladies'.
'lollipop'+'ladies'='LOLLIPOP LADIES'

'when' is the link.

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