Welsh anthem in an unfinished arrangement (5)
I believe the answer is:
neath
'unfinished arrangement' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'welsh anthem in an' is the wordplay.
I cannot quite understand how this works, but
'an' could be 'a' and 'a' is found in the answer.
The remaining letters 'neth' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for neath that I've seen before include "Under (poetic)" , "Under, poetically" , "River" , "Welsh team" , "Lower than - a town in West Glamorgan" .)