A European accepts British gymnast (7)
I believe the answer is:
acrobat
'gymnast' is the definition.
(acrobat is a kind of gymnast)
'a european accepts british' is the wordplay.
'european' becomes 'croat' (person from Croatia).
'accepts' means one lot of letters goes inside another.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'croat' placed around 'b' is 'crobat'.
'a'+'crobat'='ACROBAT'
(Other definitions for acrobat that I've seen before include "Athletic type" , "circus artiste" , "Circus gymnast" , "Performer of great agility and coordination" , "Tumbler" .)