Analyse syntactically (5)
I believe the answer is:
parse
'analyse syntactically' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for parse that I've seen before include "Resolve the structure of a sentence" , "Deconstruct grammatically" , "Analyse sentence" , "Reaps (anag.)" , "Resolve (a sentence) into its constituent parts" .)