Giddy where one is president (10)
I believe the answer is:
eisenhower
'president' is the definition.
(I've seen this before)
'giddy where one is' is the wordplay.
'giddy' is an anagram indicator.
'where'+'one'+'is'='whereoneis'
'whereoneis' anagrammed gives 'EISENHOWER'.
(Other definitions for eisenhower that I've seen before include "US president nineteen fifty three to nineteen sixty one" , "General, President, 'Ike'" , "American general" , "US president and general" , "1950s president" .)