Furthest off the mark with last two in Toughie (6)
I believe the answer is:
widest
'furthest off the mark with last two in toughie' is the definition.
I can't tell whether this definition defines the answer.
'off the mark with last two in toughie' is the wordplay.
'off the mark' becomes 'wide' (I've seen this before).
'with last two in toughie' becomes 'st' (I can't explain this - if you can you should give a lot more credence to this answer).
'wide'+'st'='WIDEST'
Can you help me to learn more?
(Other definitions for widest that I've seen before include "least slim" , "most unplayable for batsman?" , "Most broad" , "Broadest" , "most spacious" .)