Always entertained by Guinevere (4)
I believe the answer is:
ever
'always' is the definition.
(synonyms)
'entertained by guinevere' is the wordplay.
'entertained by' indicates a hidden word (the clue hosts or entertains the answer).
'EVER' is hidden in the letters of 'guinevere'.
(Other definitions for ever that I've seen before include "Continually" , "Possibly" , "At all times, always" , "On any occasion" , "constantly" .)