Having two equal sides (9)
I believe the answer is:
isosceles
'having two equal sides' 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" , "Describing a triangle with two equal sides" , "(Of triangles) having two sides the same" , "Triangle with two sides of equal length" , "Of triangular, with two sides of equal length" .)