A Balkan national hugs British gymnast (7)
I believe the answer is:
acrobat
'gymnast' is the definition.
(acrobat is a kind of gymnast)
'a balkan national hugs british' is the wordplay.
'balkan national' becomes 'croat'.
'hugs' indicates putting letters inside.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'croat' enclosing 'b' is 'crobat'.
'a'+'crobat'='ACROBAT'
(Other definitions for acrobat that I've seen before include "Circus star" , "Taco bar (anag.)" , "Gymnastic entertainer" , "Circus gymnast" , "Circus athlete" .)