State is probing established writer (8)
I believe the answer is:
essayist
'writer' is the definition.
(essayist is a kind of writer)
'state is probing established' is the wordplay.
'state' becomes 'say' ('say' can be a synonym of 'state'**).
'probing' is an insertion indicator (probe can mean to make a hole in).
'established' becomes 'est' (I've seen this in other clues).
'say'+'is'='sayis'
'sayis' inserted into 'est' is 'ESSAYIST'.
(Other definitions for essayist that I've seen before include "The venturer" , "kind of writer" , "Writer such as Addison" , "Writer (e.g. Lamb)" , "I write" .)