Italian poet, losing head, getting upset - a source of disturbance in Italy (4)
I believe the answer is:
etna
'a source of disturbance in italy' is the definition.
(Italian volcano)
'italian poet losing head getting upset' is the wordplay.
'italian poet' becomes 'dante' (Dante Alighieri).
'losing head' means to remove the first letter.
'getting upset' says the letters should be written backwards.
'dante' with its first letter taken away is 'ante'.
'ante' backwards is 'ETNA'.
(Other definitions for etna that I've seen before include "high peak" , "one blowing top?" , "Neat class of volcano in Sicily" , "Mount . . . . is a volcano in Sicily" , "smoker in Sicily" .)