Martin travelled the district (6)
I believe the answer is:
antrim
'district' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see an association between them that I can't see?
'martin travelled' is the wordplay.
'travelled' indicates an anagram.
'martin' is an anagram of 'ANTRIM'.
'the' is the link.
Can you help me to learn more?
(Other definitions for antrim that I've seen before include "County of Northern Ireland" , "18 down in Ulster" , "town in Ireland" , "Giant's Causeway county" , "Irish county of musically green glens" .)