Vigilant, watchful (5)

I believe the answer is:

alert

I believe this is a double definition.

'vigilant' is the first definition.
(similar in meaning)

'watchful' is the second definition.
(similar in meaning)

(Other definitions for alert that I've seen before include "Lively" , "On one's toes" , "Wide-awake and watchful" , "In state of watchfulness" , "Watchful, sharp" .)

I've seen this clue in The Guardian.

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