Little image I doctored that's improper (12)
I believe the answer is:
illegitimate
'improper' is the definition.
(thesaurus)
'little image i doctored' is the wordplay.
'doctored' is an anagram indicator.
'little'+'image'+'i'='littleimagei'
'littleimagei' with letters rearranged gives 'ILLEGITIMATE'.
'that's' acts as a link.
(Other definitions for illegitimate that I've seen before include "Not proper, acceptable" , "Not allowed" , "Not in accordance with the law" , "Improper" , "Unlawful, invalid" .)