Letters to an FBI man in Wales (5)
I believe the answer is:
dyfed
'wales' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's a link between them I don't understand?
'letters to an fbi man' is the wordplay.
'letters' becomes 'dy' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to an fbi man' becomes 'fed' (term for an FBI agent).
'dy'+'fed'='DYFED'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for dyfed that I've seen before include "Old Welsh county" , "Area of Wales" , "part of Wales" , "Carmarthen area?" , "one of the old county set" .)