Bill allowed some medication (6)
I believe the answer is:
tablet
'some medication' is the definition.
(tablet is a kind of medication)
'bill allowed' is the wordplay.
'bill' becomes 'tab' (a tab is a bill at a bar).
'allowed' becomes 'let' (to let is to allow or permit).
'tab'+'let'='TABLET'
(Other definitions for tablet that I've seen before include "Small bar of soap" , "Handheld personal computer" , "Pill; computer" , "Battle (anag) - pill" , "Prescription" .)