Teacher varied changes to keep close to syllabus (7)
I believe the answer is:
adviser
'teacher' is the definition.
(thesaurus)
'varied changes to keep close to syllabus' is the wordplay.
'changes' indicates anagramming the letters.
'to keep' is an insertion indicator.
'close to' indicates one should take the final letters (the close/ending of).
The final letter of 'syllabus' is 's'.
'varied' with letters rearranged gives 'advier'.
'advier' placed around 's' is 'ADVISER'.
(Other definitions for adviser that I've seen before include "Guide" , "ID saver (anag.)" , "Counseller" , "Counsellor, mentor" , "subject's specialist consultant" .)