23 across
Power
failure
abroad
goes
on
a
long
time
(6)
Power failure abroad goes on a long time (6)
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The whole clue is the definition (& lit or double definition).
How the clue works
Power failure is your definition — a loss of electrical supply. Then the wordplay backs it up: abroad gives you OUT (as in "out of the country") and a long time gives you AGE, and you just stick them together.