System of words (8)
I believe the answer is:
language
'system of words' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for language that I've seen before include "Tongue" , "Eg, French, German" , "Glue a nag, wrongly, to speak it" , "Eg, Italian" , "English or Irish, say" .)