Significant foreigner entering street (7)
I believe the answer is:
salient
'significant' is the definition.
(thesaurus)
'foreigner entering street' is the wordplay.
'foreigner' becomes 'alien' ('alien' can be a synonym of 'foreigner').
'entering' 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 "part of defences" , "Entails (anag) - most important" , "Prominent, most noticeable" , "Projecting outwards; significant" , "Conspicuous; pointing outwards" .)