Fragrance of a capital (in local parlance) (5)
I believe the answer is:
aroma
'fragrance' is the definition.
(synonyms)
'a capital in local parlance' is the wordplay.
'capital in local parlance' becomes 'roma' (Italian name for Rome).
'a'+'roma'='AROMA'
'of' acts as a link.
(Other definitions for aroma that I've seen before include "Savour" , "Scent - fragrance" , "Test of knowledge" , "Distinctive odour" , "Stink" .)