Eldest of the Baldwin brothers
I believe the answer is:
alec
'eldest of the baldwin brothers' 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 "A smart . . . . is a know-all in lace" , "Actor Guinness is smart" , "Sir - Douglas-Home, former PM" , "Smart man?" , "Guinness (a smart lad?)" .)