System of coats of arms (8)
I believe the answer is:
heraldry
'system of coats of arms' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for heraldry that I've seen before include "The study of armorial bearings" , "Classification of armorial bearings" , "study of insignia" , "Armorial system" , "The study of crests and genealogies" .)