Capital that's crazy and free (6)
I believe the answer is:
madrid
'capital' is the definition.
(capital of Spain)
'crazy and free' is the wordplay.
'crazy' becomes 'mad' (synonyms).
'and' says to put letters next to each other.
'free' becomes 'rid' (to be free of something is to be rid of it).
'mad'+'rid'='MADRID'
'that's' acts as a link.
(Other definitions for madrid that I've seen before include "City with the Prado national art gallery" , "Spanish city" , "Capital of Spain since 1561" , "European capital city" , "Spain's capital" .)