In great condition in boxing match (8,3)
I believe the answer is:
fighting fit
'in' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'great condition in boxing match' is the wordplay.
'great condition' becomes 'ing' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'boxing' becomes 'fight' (fight is a kind of boxing).
'match' becomes 'fit' (synonyms).
'fight'+'fit'='fightfit'
'ing' placed within 'fightfit' is 'FIGHTING FIT'.
Can you help me to learn more?
(Other definitions for fighting fit that I've seen before include "In excellent health" , "in good shape" , "very well" , "In great form" , "Standing up to attack of illness" .)