Heaving from ship in motion ceases — sinks, unfortunately (11)
I believe the answer is:
seasickness
'heaving from ship in motion' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'ceases sinks unfortunately' is the wordplay.
'unfortunately' indicates anagramming the letters.
'ceases'+'sinks'='ceasessinks'
'ceasessinks' is an anagram of 'SEASICKNESS'.
Can you help me to learn more?
(Other definitions for seasickness that I've seen before include "Marine nausea" , "Mal de mer" .)