Facsimile I put on record mistakenly (12)
I believe the answer is:
reproduction
'facsimile' is the definition.
(thesaurus)
'i put on record mistakenly' is the wordplay.
'mistakenly' is an anagram indicator.
'i'+'put'+'on'+'record'='iputonrecord'
'iputonrecord' is an anagram of 'REPRODUCTION'.
(Other definitions for reproduction that I've seen before include "Picture" , "hardly original" , "sound quality" , "Print made of a painting" , "Having a family" .)