Guinness who played Obi-Wan Kenobi (4)
I believe the answer is:
alec
'guinness who played obi-wan kenobi' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alec that I've seen before include "Boy's name (a smart one?)" , "Sir -- Guinness, actor" , "A smart . . . . is a know-all in lace" , "Guinness (a smart lad?)" , "Smart boy?" .)