Vital work by a new foreigner (7)
I believe the answer is:
latvian
'new foreigner' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'vital work by a' is the wordplay.
'work' is an anagram indicator.
'by' is a charade indicator (letters next to each other).
'a' becomes 'an'.
'vital' with letters rearranged gives 'latvi'.
'latvi'+'an'='LATVIAN'
Can you help me to learn more?
(Other definitions for latvian that I've seen before include "Riga resident" , "Eg, native of Riga" , "European national" , "One from Riga" , "Baltic national" .)