"Holy cow!” (5)
(Other definitions for yikes that I've seen before include "alarmed expression" , "Expression of alarm or astonishment" , "Watch out" , "Exclamation of surprise or alarm" , "Gosh! - Oh no!" .)
(Other definitions for egad that I've seen before include "Old oath" , "Oath sworn" , "Old exclamation; aged (anagram)" , "Forgotten curse" , "Archaic exclamation of surprise" .)
'holy cow' is the definition.
(both are expressions of surprise)
This is all the clue.
(Other definitions for gee that I've seen before include "Gracious" , "American exclamation" , "Mild exclamation" , "Word of encouragement to a horse" , "Alphabet's seventh letter" .)