Conspicuous, foreigner in street (7)
I believe the answer is:
salient
'conspicuous' is the definition.
(similar in meaning)
'foreigner in street' is the wordplay.
'foreigner' becomes 'alien' (synonyms).
'in' indicates putting letters inside.
'street' becomes 'st' (abbreviation).
'alien' put inside 'st' is 'SALIENT'.
(Other definitions for salient that I've seen before include "Outstanding - it's lean (anag)" , "Entails being most noticeable" , "Prominent, most noticeable" , "obvious" , "Foremost" .)