24 across
Messenger’s
very
good
memory
about
outing
(10)
Messenger’s very good memory about outing (10)
hints
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The definition is at the beginning of the clue.
How the clue works
Messenger is the definition — specifically the cheeky sort. The wordplay takes SO ('very good'), G ('good'), and RAM ('computer memory') to give SOGRAM, then slots TRIP ('outing') inside after the S to produce the full ten-letter answer.