Stand for leadership of the youth party in free Yugoslavia (6)
I believe the answer is:
typify
'stand for' is the definition.
(both can mean to represent or epitomise)
'leadership of the youth party in free yugoslavia' is the wordplay.
'leadership of' indicates taking the first letters (the letters which lead the words).
The first letters of 'the youth party in free yugoslavia' is 'TYPIFY'.
(Other definitions for typify that I've seen before include "Exemplify" , "Characterise" , "Symbolise" , "Be characteristic of" , "Represent" .)