Official works with Conservative before being unmasked (5)
I believe the answer is:
canon
'official works' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'conservative before being unmasked' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'before' says to put letters next to each other.
'being unmasked' becomes 'anon' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'c'+'anon'='CANON'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for canon that I've seen before include "Part of chapter" , "set of books" , "senior cleric" , "General principle or senior priest" , "Literary works of quality" .)