Alpinist injured in uncontrolled descent (8)
I believe the answer is:
tailspin
'uncontrolled descent' is the definition.
'alpinist injured' is the wordplay.
'injured' is an anagram indicator.
'alpinist' anagrammed gives 'TAILSPIN'.
'in' acts as a link.
(Other definitions for tailspin that I've seen before include "Spiral aeroplane dive" , "Spiral dive of aircraft in trouble" , "Alpinist (anag) -- state of panic" , "awful state" , "Chaotic situation" .)