Suppose visitors to be short of time (5)
I believe the answer is:
guess
'suppose' is the definition.
(I know that suppose can be written as guess)
'visitors to be short of time' is the wordplay.
'visitors' becomes 'guests' (guest is a kind of visitor).
'to be short of' is a deletion indicator.
'time' becomes 't' (abbreviation).
'guests' with 't' taken away is 'GUESS'.
(Other definitions for guess that I've seen before include "Fancy" , "Divine - estimate" , "Speculation" , "Conjecture - estimate" , "Estimate, supposition" .)