Clause relates to a particular thing (7)
I believe the answer is:
article
'clause' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for article that I've seen before include "'The', definitely" , "Newspaper essay" , "A rewritten piece" , "Rile cat (anag.)" , "Division" .)