Crossword Genius

Flash Croatian deputy? (5,6)

Ross

I believe the answer is:

split second

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This clue could be a double definition.

'flash' is the first definition.
(I know that flash can be written as split second)

'croatian deputy?' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

Can you help me to learn more?

(Other definitions for split second that I've seen before include "Twinkling of an eye" , "Very little time" , "Instant" , "An extremely short time" , "Very brief moment of time" .)

I've seen this clue in The Times.
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