Incautious (8)
I believe the answer is:
careless
'incautious' is the definition.
(associated in meaning)
This is the entire clue.
(Other definitions for careless that I've seen before include "Unthinking and irresponsible" , "Inattentive to one's work" , "Not careful or thorough enough" , "'Thoughtless, inattentive (8)'" , "Lax" .)