Part of treatment for Jack's brother to have daily (5,5)
I believe the answer is:
brown paper
'part of treatment for jack's' is the definition.
('With vinegar and brown paper' from Jack and Jill)
'brother to have daily' is the wordplay.
'brother' becomes 'br' (abbreviation in titles of monks).
'to have' becomes 'own' (to have something is to own it).
'daily' becomes 'paper' (newspaper).
'br'+'own'+'paper'='BROWN PAPER'
(Other definitions for brown paper that I've seen before include "It's used for wrapping" , "Parcel wrapping" .)