Unprepared, I’m seen at concert, put out (9)
I believe the answer is:
impromptu
'unprepared' is the definition.
(impromptu means improvised or unprepared)
'i'm seen at concert put out' is the wordplay.
'seen at' means one lot of letters go next to another.
'concert' becomes 'prom' (abbreviation for promenade concert).
'out' indicates an anagram (out can mean wrong or inaccurate).
'put' with letters rearranged gives 'ptu'.
'im'+'prom'+'ptu'='IMPROMPTU'
(Other definitions for impromptu that I've seen before include "piece by Chopin, perhaps" , "Without rehearsal or preparation" , "Without much planning" , "Ad hoc: spontaneous-sounding musical piece mastered by Schubert" , "Extempore" .)