Royal informer with a series of blunders (6)
I believe the answer is:
errata
'series of blunders' is the definition.
Although both the answer and definition are plural nouns, I don't see how one could define the other.
'royal informer with a' is the wordplay.
'royal' becomes 'er' (I've seen this in other clues).
'informer' becomes 'rat' (synonyms).
'with' says to put letters next to each other.
'er'+'rat'+'a'='ERRATA'
Can you help me to learn more?
(Other definitions for errata that I've seen before include "Noted mistakes" , "Misprints in a book" , "Mistakes in printed proofs" , "List of text corrections to be made in a publication" , "List of printed mistakes" .)