Buccaneer loses his head, getting angry (5)
I believe the answer is:
irate
'angry' is the definition.
(irate can mean angry or annoyed)
'buccaneer loses his head' is the wordplay.
'buccaneer' becomes 'pirate' (a buccaneer is a pirate).
'loses his head' means to remove the first letter.
'pirate' with its first letter taken away is 'IRATE'.
'getting' is the link.
(Other definitions for irate that I've seen before include "Boiling" , "Angry, annoyed" , "Wild" , "Angry, enraged" , "Cross, irritated" .)