Most unconvincing charge by leading barrister in case (8)
I believe the answer is:
feeblest
'most unconvincing' is the definition.
Both the answer and definition are superlative adjectives. Perhaps you can see a link between them that I can't see?
'charge by leading barrister in case' is the wordplay.
'charge by' becomes 'fee' (fee is a kind of charge. I am not sure about the 'by' bit.).
'leading' says to take the initial letters.
'in case' becomes 'lest' (I've seen this in another clue).
The initial letter of 'barrister' is 'b'.
'fee'+'b'+'lest'='FEEBLEST'
Can you help me to learn more?
(Other definitions for feeblest that I've seen before include "Most ineffective" , "most faint" , "Most pathetic" , "Most inadequate" .)