Decline drink (4)
I believe the answer is:
sink
I believe this is a double definition.
'decline' is the first definition.
(I know that sink is a more specific form of drop)
'drink' is the second definition.
(I've seen this before)
(Other definitions for sink that I've seen before include "Get worse" , "Plunge down" , "place of iniquity?" , "drink" , "Plumbing fixture" .)