No domain in a reformation of the present era (4,6)
I believe the answer is:
anno domini
'the present era' is the definition.
The definition suggests a singular noun which matches the answer.
'no domain in a reformation' is the wordplay.
'a reformation' indicates anagramming the letters.
'no'+'domain'+'in'='nodomainin'
'nodomainin' anagrammed gives 'ANNO DOMINI'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for anno domini that I've seen before include "In the year of our Lord" , "having a date, she may put it on" , "Advancing old age (informal)" , "AD in full" , "later days" .)