Fit after trailing badly (4,6)
I believe the answer is:
well behind
'badly' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'fit after trailing' is the wordplay.
'fit' becomes 'well' (associated in meaning).
'after' becomes 'behind' (as in coming after or behind someone else).
'trailing' says to put letters next to each other.
'well'+'behind'='WELL BEHIND'
Can you help me to learn more?
(Another definition for well behind that I've seen is " in a desperate situation!".)