A journal is probing dope defender (9)
I believe the answer is:
apologist
'defender' is the definition.
(I've seen this before)
'a journal is probing dope' is the wordplay.
'journal' becomes 'log' (I've seen this in another clue).
'probing' means one lot of letters goes inside another (probe can mean to make a hole in).
'dope' becomes 'pot' (both can informally mean cannabis).
'log'+'is'='logis'
'logis' going within 'pot' is 'pologist'.
'a'+'pologist'='APOLOGIST'
(Other definitions for apologist that I've seen before include "One defending the controversial" , "Person who argues to defend or justify some policy" , "Advocate" , "One who argues in favour of something controversial" , "Someone arguing" .)