Dull hack? No, an inspired writer (7)
I believe the answer is:
matthew
'writer' is the definition.
(I have seen 'Good writer' mean 'matthew' so perhaps 'writer' could also mean 'matthew')
'dull hack?' is the wordplay.
'dull' becomes 'matt' (similar in meaning).
'hack?' becomes 'hew' (I've seen this in another clue).
'matt'+'hew'='MATTHEW'
'no an inspired' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for matthew that I've seen before include "Apostle to whom the first Gospel is ascribed" , "He's a saint" , "Scripture" , "Arnold, for example" , "Gospel writer" .)