Incautious knight (8)
I believe the answer is:
cavalier
I believe this is a double definition.
'incautious' is the first definition.
(I've seen this before)
'knight' is the second definition.
(I've seen this before)
(Other definitions for cavalier that I've seen before include "Supercilious - old Royalist" , "'Thoughtless, offhand (8)'" , "Shout out noisily" , "Haughty" , "Civil War participant" .)