The queasiness is bad: the sea I find rough (7)
I believe the answer is:
malaise
'rough' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'the queasiness is bad the sea i' is the wordplay.
'the queasiness' becomes 'mal' (I can't justify this - if you can you should believe this answer much more).
'is bad' indicates an anagram (I've seen 'being bad' mean this).
'sea'+'i'='seai'
'seai' with letters rearranged gives 'aise'.
'mal'+'aise'='MALAISE'
'find' is the link.
Can you help me to learn more?
(Other definitions for malaise that I've seen before include "Uneasy feeling" , "Disquiet" , "depression" , "General feeling of unease or illness" , "Feeling of physical or mental illness" .)