Branch of linguistics (9)
I believe the answer is:
semantics
'branch of linguistics' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for semantics that I've seen before include "The meaning attached to words" , "Branch of linguistics to do with meaning" , "The significance of a text" , "Main sects (anag.)" , "Branch of linguistics concerned with meanings" .)