Neglect Dad's drink (4,2)
I believe the answer is:
pass up
'neglect' is the definition.
(I've seen this before)
'dad's drink' is the wordplay.
'dad's' becomes 'pa's' (both can mean one's father).
'drink' becomes 'sup' (to sup is to drink).
'pas'+'sup'='PASS UP'
(Other definitions for pass up that I've seen before include "Have nothing to do with" , "Refrain from seizing (an opportunity)" , "forego" , "Turn (something) down" , "Refrain from taking an opportunity" .)