Writer, monster, has ancient title (9)
I believe the answer is:
pendragon
'ancient title' is the definition.
The definition suggests a singular noun which matches the answer.
'writer monster' is the wordplay.
'writer' becomes 'pen' (something which writes).
'monster' becomes 'dragon' (dragon is a kind of monster).
'pen'+'dragon'='PENDRAGON'
'has' is the link.
Can you help me to learn more?
(Other definitions for pendragon that I've seen before include "Uther --" , "King Arthur, for example" , "Ruler" , "Tribal chief," , "old British chief" .)