System of names (12)
I believe the answer is:
nomenclature
'system of names' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for nomenclature that I've seen before include "System involving naming" , "Classified system of names" , "Neater column (anag) - terminology" , "Particular terminology - near Uncle Tom (anag)" , "list of names" .)