An angle between 90 and 180 degrees (6)
I believe the answer is:
obtuse
'an angle between 90 and 180 degrees' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for obtuse that I've seen before include "A stupid angle?" , "Dull or blunt" , "boneheaded?" , "Thick, blunt" , "Mentally slow - kind of angle" .)