Thrill ride cry (4)
I believe the answer is:
whee
'thrill ride cry' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for whee that I've seen before include "Exclamation of excitement when going fast" , "Exuberant cry" , "Expression of delight" , "What fun" , "I'm going downhill, fast!" .)