Striking foreigner in street (7)
I believe the answer is:
salient
'striking' is the definition.
(I know that striking can be written as salient)
'foreigner in street' is the wordplay.
'foreigner' becomes 'alien' (synonyms).
'in' indicates putting letters inside.
'street' becomes 'st' (abbreviation).
'alien' put into 'st' is 'SALIENT'.
(Other definitions for salient that I've seen before include "obvious" , "Entails (anag) - most important" , "defence work" , "Outstanding - it's lean (anag)" , "Foremost" .)