Eccentric mentions a US state (9)
I believe the answer is:
minnesota
'us state' is the definition.
(I've seen this before)
'eccentric mentions a' is the wordplay.
'eccentric' is an anagram indicator.
'mentions' is an anagram of 'minnesot'.
'minnesot'+'a'='MINNESOTA'
(Other definitions for minnesota that I've seen before include "Nominates the strange state" , "Nominates for American state" , "Superior neighbour" , "Wobegon state (Keillor)" , "American state, capital St Paul" .)