Sides of a gem (6)
I believe the answer is:
facets
'sides of a gem' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for facets that I've seen before include "Surfaces or aspects" , "Sides or aspects, diamonds or buildings" , "Sides or surfaces" , "Sides of a cut gemstone" , "Faces of cut gemstones" .)