Uncontrolled descent of alpinist taking a tumble (8)
I believe the answer is:
tailspin
'uncontrolled descent' is the definition.
(uncontrolled descent of an aircraft)
'alpinist taking a tumble' is the wordplay.
'taking a tumble' indicates an anagram.
'alpinist' with letters rearranged gives 'TAILSPIN'.
'of' is the link.
(Other definitions for tailspin that I've seen before include "confused state" , "Alpinist (anag) -- state of panic" , "that could result in crash" , "awful state" , "Chaotic situation" .)