Relation of Swiss folk hero in German capital (7)
I believe the answer is:
telling
'relation' is the definition.
(to relate a story is to tell it)
'swiss folk hero in german capital' is the wordplay.
'swiss folk hero' becomes 'tell' (William Tell).
'capital' suggests taking the first letters.
The initial letter of 'german' is 'g'.
'tell'+'in'+'g'='TELLING'
'of' is the link.
(Other definitions for telling that I've seen before include "Effective - narration" , "of significance" , "Counting" , "briefing" , "Powerful; relating" .)