Striking foreigner encountered in street (7)
I believe the answer is:
salient
'striking' is the definition.
('salient' can be a synonym of 'striking')
'foreigner encountered in street' is the wordplay.
'foreigner' becomes 'alien' ('alien' can be a synonym of 'foreigner').
'encountered in' means one lot of letters goes inside another.
'street' becomes 'st'.
'alien' going inside 'st' is 'SALIENT'.
(Other definitions for salient that I've seen before include "obvious" , "Entails (anag) - most important" , "Projecting outwards; significant" , "Entails being most noticeable" , "Foremost" .)