Mother is not by the sea on the continent (8)
I believe the answer is:
mainland
'sea on the continent' is the definition.
The answer and definition can be both natural objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'mother is not by' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'is not by' becomes 'inland' (I can't explain this - if you can you should give a lot more credence to this answer).
'ma'+'inland'='MAINLAND'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for mainland that I've seen before include "Principle country, not an island" , "Area excluding offshore islands" , "Country or continent, as distinguished from an island" , "A country's principal as opposed to its islands" , "Part of territory excluding offshore islands" .)