Reckon visitors need time to leave (5)

I believe the answer is:

guess

I'm a little stuck... Click here to teach me more about this clue!

'reckon' is the definition.
(I know that reckon can be written as guess)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for guess that I've seen before include "Dare say" , "Speculate" , "Estimate on the basis of little information" , "Make stab at" , "shot?" .)

I've seen this clue in The Times and The Sunday Times.

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