Unintentionally (12)
There are a few possibilities for this:
accidentally
'unintentionally' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for inadvertently that I've seen before include "In an unguarded moment" , "By accident" , "Accidentally" .)
'unintentionally' is the definition.
(thesaurus)
This is the entire clue.
'unintentionally' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for accidentally that I've seen before include "Not purposefully, by mistake" , "Inadvertently, by chance" .)