Undistinguished male going out in cape (8)
I believe the answer is:
nameless
'undistinguished' is the definition.
(thesaurus)
'male going out in cape' is the wordplay.
'going out' indicates anagramming the letters (out can mean wrong or inaccurate).
'in' is an insertion indicator.
'cape' becomes 'ness' (synonyms).
'male' anagrammed gives 'amel'.
'amel' inserted into 'ness' is 'NAMELESS'.
(Other definitions for nameless that I've seen before include "Untitled" , "Salesmen lacking identity" , "Lacking means of identification" , "like the guy in the spaghetti movies?" , "Too horrific to be described" .)