Wilier boxers score for the poor fellow (6)
I believe the answer is:
wretch
'the poor fellow' is the definition.
(poor or unfortunate person)
'wilier boxers score' is the wordplay.
'wilier boxers' becomes 'wr' (I can't explain this - if you can you should believe this answer much more).
'score' becomes 'etch' (etch can mean to score or carve into something).
'wr'+'etch'='WRETCH'
'for' is the link.
Can you help me to learn more?
(Other definitions for wretch that I've seen before include "Poor, pitiable person" , "Miserable fellow" , "Someone you feel sorry for" , "Good-for-nothing" , "A poor miserable person" .)