Crush spirit -- it's over (6)
I believe the answer is:
stifle
'crush' is the definition.
(thesaurus)
'spirit it's over' is the wordplay.
'spirit' becomes 'elf' (I've seen this before).
'over' says the letters should be written in reverse.
'elf'+'its'='elfits'
'elfits' back-to-front is 'STIFLE'.
(Other definitions for stifle that I've seen before include "Suppress or suffocate" , "Quash" , "Smother - 6 down (anag)" , "Asphyxiate - itself (anag)" , "Silence" .)