Witnesses host set table back a bit (7)
I believe the answer is:
attests
'witnesses' is the definition.
(I've seen this in another clue)
'host set table back a bit' is the wordplay.
'a bit' indicates a hidden word (the answer is formed by a bit of the clue).
'back' says the letters should be written backwards.
'stsetta' is hidden in the letters of 'host set table'.
'stsetta' written backwards gives 'ATTESTS'.
(Other definitions for attests that I've seen before include "Sat test (anag.)" , "Authenticates or affirms to be true" , "Certifies" , "Gives evidence in court" , "Bears witness" .)