Believe visitors will be short of time (5)
I believe the answer is:
guess
'believe' is the definition.
(thesaurus)
I don't 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" , "Speculation" , "Estimate; suppose" , "Take a stab at the answer" , "Conjecture - estimate" .)