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