Emperor penguins are rarely especially active taking just seconds at sea (6)

I believe the answer is:

caesar

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'emperor' is the definition.
(title used by Roman emperors)

I don't understand how the remainder of the clue works.

(Other definitions for caesar that I've seen before include "Julius, stabbed by Brutus" , "See 13 Across" , "See 12" , "Roman dictator" , "Emperor of ancient Rome, like Julius" .)

I've seen this clue in The Guardian.

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