Precisely how is half of a tenancy agreement addressed? (2,3,6)

I believe the answer is:

to the letter

I'm a little stuck... Click here to teach me more about this clue!

'precisely' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for to the letter that I've seen before include "correct in every detail" , "strictly speaking" , "Following every detail" , "With adherence to strict detail" , "Accurately" .)

I've seen this clue in The Everyman puzzle in The Observer.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.