Jerk mentions a US state (9)
I believe the answer is:
minnesota
'us state' is the definition.
(I've seen this before)
'jerk mentions a' is the wordplay.
'jerk' is an anagram indicator.
'mentions' with letters rearranged gives 'minnesot'.
'minnesot'+'a'='MINNESOTA'
(Other definitions for minnesota that I've seen before include "Superior neighbour" , "US state, capital St Paul" , "Nominates for American state" , "US state -. of Iowa" , "source of iron ore" .)