Chief cry used by American parachutists (8)
I believe the answer is:
geronimo
This clue might be a double definition.
'chief' is the first definition.
(I've seen this before)
'cry used by american parachutists' is the second definition.
'geronimo' can be an answer for 'cry' (I have seen 'exhilarated cry' mean 'geronimo' so perhaps 'cry' could also mean 'geronimo'). I am unsure of the 'used by american parachutists' bit.
Can you help me to learn more?
(Other definitions for geronimo that I've seen before include "Whee!; Apache chief" , "Famous Apache chieftain" , "I'm no ogre like famous Apache Indian chief" , "Apache chieftain - US paratroopers war cry when jumping" , "cry from bungee jumper?" .)