Very good speed for buccaneer (6)
I believe the answer is:
pirate
'buccaneer' is the definition.
(historical term for a pirate)
'very good speed' is the wordplay.
'very good' becomes 'pi' (pi can mean pious).
'speed' becomes 'rate' (the speed at which something happens).
'pi'+'rate'='PIRATE'
'for' is the link.
(Other definitions for pirate that I've seen before include "Criminal on the high seas" , "Sea raider" , "plagiarist" , "Copyright infringer" , "Plagiarise" .)