Exclamation a horse may understand (3)
I believe the answer is:
gee
'exclamation' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for gee that I've seen before include "Exclamation of surprise" , "Urge horse - expression of surprise" , "Mild exclamation" , "Wow!" , "Expression of mild surprise (mainly US)" .)