A routine king wasted with unknown divergence (7)
I believe the answer is:
anomaly
'divergence' is the definition.
(thesaurus)
'a routine king wasted with unknown' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is found within the answer.
'unknown' could be 'y' (algebra) and 'y' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for anomaly that I've seen before include "Deviation from the norm or common" , "Unexpected result" , "eccentricity" , "Deviation from the norm or expected" , "Out-of-line result" .)