Inexperience of amateur seen in event I arranged (7)
I believe the answer is:
naivete
'inexperience' is the definition.
(thesaurus)
'amateur seen in event i arranged' is the wordplay.
'amateur' becomes 'a'.
'seen in' is an insertion indicator.
'arranged' is an anagram indicator.
'event'+'i'='eventi'
'eventi' is an anagram of 'nivete'.
'a' inserted inside 'nivete' is 'NAIVETE'.
'of' acts as a link.
(Other definitions for naivete that I've seen before include "Quality of the simple" , "natural simplicity" , "Innocence, artlessness" , "lack of experience" , "Greenness" .)