Boxer observed accepting inadmissible payment method (8)
I believe the answer is:
southpaw
'boxer' is the definition.
(term for a left-handed boxer)
'observed accepting inadmissible payment method' is the wordplay.
'observed' becomes 'saw' (seen).
'accepting' indicates putting letters inside (inserted letters are accepted).
'inadmissible' becomes 'out'.
'payment method' becomes 'hp' (I can't justify this - if you can you should give a lot more credence to this answer).
'out'+'hp'='outhp'
'saw' enclosing 'outhp' is 'SOUTHPAW'.
Can you help me to learn more?
(Other definitions for southpaw that I've seen before include "A left-handed boxer who leads with the right" , "Boxer who leads with right fist" , "one leading from the right" , "Left-handed pugilist" , "Left-handed person, especially a boxer" .)