Not an intelligent sort of angle? (6)
I believe the answer is:
obtuse
'sort of angle?' is the definition.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for obtuse that I've seen before include "Slow-witted; type of angle" , "Mentally slow - kind of angle" , "Lacking in insight" , "Blunt, dull-witted" , "(Of angle) between 90deg and 180deg - dull" .)