Part not including drinking water, ultimately (7)
I believe the answer is:
excerpt
'part' is the definition.
(I have seen 'part of programme' mean 'excerpt' so perhaps 'part' could also mean 'excerpt')
'not including drinking water ultimately' is the wordplay.
'not including' becomes 'except' (I've seen this before).
'drinking' means one lot of letters goes inside another (inserted letters are consumed or drunk).
'water ultimately' becomes 'r' (I've seen this in other clues).
'except' placed around 'r' is 'EXCERPT'.
(Other definitions for excerpt that I've seen before include "Passage cut" , "Short extract" , "Passage taken from a larger work" , "Quote" , "Extract from book or film" .)