It’s in the north of England, not the heart of Tyrone (4)
I believe the answer is:
tyne
'tyrone' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I don't see?
'it's in the north of england not the heart' is the wordplay.
'it's in the' indicates putting letters inside.
'north of england' becomes 'tye' (I can't explain this - if you can you should give a lot more credence to this answer).
'not' becomes 'tonup' (I've seen this before).
'the heart' indicates the central letters.
The central letter of 'tonup' is 'n'.
'tye' enclosing 'n' is 'TYNE'.
'of' is the link.
Can you help me to learn more?
(Other definitions for tyne that I've seen before include "River running through Newcastle" , "Newcastle's river" , "English river" , "River at Gateshead" , "Flower" .)