It's wrong to confuse Mike with Stan (8)
I believe the answer is:
mistaken
'it's wrong' is the definition.
(similar in meaning)
'confuse mike with stan' is the wordplay.
'confuse' is an anagram indicator.
'with' says to put letters next to each other.
'mike'+'stan'='mikestan'
'mikestan' is an anagram of 'MISTAKEN'.
'to' is the link.
(Other definitions for mistaken that I've seen before include "Wrong-headed" , "Wrongly understood" , "Erroneous" , "Wrong (in judgement)" , "'Wrong, misguided (8)'" .)