Arresting foreigner who's in the way (7)
I believe the answer is:
salient
'arresting' is the definition.
(thesaurus)
'foreigner who's in the way' is the wordplay.
'foreigner' becomes 'alien' (synonyms).
'who's in' means one lot of letters goes inside another.
'the way' becomes 'st' (abbreviation for street).
'alien' going inside 'st' is 'SALIENT'.
(Other definitions for salient that I've seen before include "defence work" , "Prominent - in tales (anag)" , "Leaping (heraldry)" , "Outstanding - it's lean (anag)" , "Prominent, striking" .)