Mark and Ian wandering on the street (5)
I believe the answer is:
stain
'mark' is the definition.
(synonyms)
'ian wandering on the street' is the wordplay.
'wandering' is an anagram indicator.
'on' indicates putting letters inside (as in clothing 'on' a person).
'the street' becomes 'st' (abbreviation).
'ian' with letters rearranged gives 'ain'.
'ain' going around 'st' is 'STAIN'.
'and' acts as a link.
(Other definitions for stain that I've seen before include "Blot" , "Satin (anag.)" , "Stigma" , "Spot - shame" , "Blemish; colour (wood)" .)