Down under, the Briton may not take my part (5)
I believe the answer is:
pommy
'down under' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I don't see?
'briton may not take my part' is the wordplay.
I cannot really see how this works, but
'briton' could be 'pom' (pom is a kind of briton) and 'pom' is found in the answer.
'my' is within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'the' is the link.
Can you help me to learn more?
(Other definitions for pommy that I've seen before include "British person (Australian colloquial)" , "Abusive term for English" , "Victorian Englishman" .)