Guinness of "The Bridge on the River Kwai" (4)
I believe the answer is:
alec
'guinness of the bridge on the river kwai' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for alec that I've seen before include "Actor Guinness is smart" , "Sir - Douglas-Home, former PM" , "Smart chap" , "Guinness (a smart lad?)" , "Smart man?" .)