Founder (4)
'founder' is the definition.
(sinking is a kind of foundering)
This is all the clue.
(Other definitions for sink that I've seen before include "Get worse" , "Subside" , "Kitchen equipment - founder" , "Excavate (a well)" , "Go down (in the kitchen?)" .)
'founder' is the definition.
(synonyms)
This is all the clue.
(Other definitions for collapse that I've seen before include "fold" , "Founder" , "Give way, fail suddenly" , "Faint and fall" , "Fall or disintergrate" .)