Kind of triangle (9)
I believe the answer is:
isosceles
'kind of triangle' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for isosceles that I've seen before include "(Of triangles) having two sides the same" , "Of triangular, with two sides of equal length" , "Kind of triangle" , "Describing a triangle with two equal sides" , "Triangle with two sides of equal length" .)