Guess at teatimes arrangement (8)
I believe the answer is:
estimate
'guess' is the definition.
(I know that guess can be written as estimate)
'teatimes arrangement' is the wordplay.
'arrangement' indicates an anagram.
'teatimes' anagrammed gives 'ESTIMATE'.
'at' acts as a link.
(Other definitions for estimate that I've seen before include "Judge the worth of" , "Judge the approximate cost of" , "Tease Tim (anag.)" , "Believe" , "Statement giving the likely cost of a job" .)