Tutor taps into very old Latin (6)
I believe the answer is:
school
'tutor' is the definition.
(thesaurus)
'taps into very old latin' is the wordplay.
'taps' becomes 'ch' (I've seen this in other clues).
'into' means one lot of letters goes inside another.
'very' becomes 'so' (both can mean 'extremely').
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'latin' becomes 'l'.
'ch' inserted inside 'so' is 'scho'.
'scho'+'o'+'l'='SCHOOL'
(Other definitions for school that I've seen before include "streaming in here?" , "Instruct" , "Teaching establishment" , "Academy; group of fish" , "Teach; group of fish" .)