Gordon Bennett's righteous misery (4,5)
I believe the answer is:
good grief
'gordon bennett's' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'righteous misery' is the wordplay.
'righteous' becomes 'good' (associated in meaning).
'misery' becomes 'grief' (I've seen this before).
'good'+'grief'='GOOD GRIEF'
Can you help me to learn more?
(Other definitions for good grief that I've seen before include "Exclamation of surprise or dismay" , "Oath given surprisingly" , "Exasperated utterance" , "I'm dismayed!" .)