Furious buccaneer loses head (5)
I believe the answer is:
irate
'furious' is the definition.
(I know that furious can be written as irate)
'buccaneer loses head' is the wordplay.
'buccaneer' becomes 'pirate' (a buccaneer is a pirate).
'loses head' means to remove the first letter.
'pirate' with its first letter removed is 'IRATE'.
(Other definitions for irate that I've seen before include "Wild" , "raging" , "become irritated" , "Extremely cross" , "Angry, annoyed" .)