"Who knew!" (5)
'who knew?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gee that I've seen before include "Wow!" , "Word of encouragement to a horse" , "Golly" , "American exclamation" , "Horse - surprised expression" .)
(Other definitions for gosh that I've seen before include "My goodness!" , "Surprised exclamation" , "expression of surprise" , "Crikey" , "Exclamation of surprise" .)