Public school boy boxing second European (8)
I believe the answer is:
estonian
'european' is the definition.
(person from Estonia)
'public school boy boxing second' is the wordplay.
'public school boy' becomes 'etonian' (I've seen this before).
'boxing' is an insertion indicator ('box' can mean contain, as in to put in a box).
'second' becomes 's' (common abbreviation).
'etonian' going around 's' is 'ESTONIAN'.
(Other definitions for estonian that I've seen before include "European language" , "Balt" , "Baltic state native" , "From Tallinn, for example" , "One from Tallinn" .)