Italian hot-head rejecting opening stake (4)
I believe the answer is:
etna
'italian hot-head' is the definition.
(Italian volcano)
'rejecting opening stake' is the wordplay.
'rejecting' says the letters should be written in reverse (I've seen 'reject' mean this).
'opening stake' becomes 'ante' (stake in poker).
'ante' backwards is 'ETNA'.
(Other definitions for etna that I've seen before include "Natural hazard" , "Neat (anag)" , "Active European volcano" , "Volcanic mount in Sicily" , "burning mountain" .)