Most important way to welcome foreigner (7)
I believe the answer is:
salient
'most important' is the definition.
(I've seen this before)
'way to welcome foreigner' is the wordplay.
'way' becomes 'st'.
'to welcome' is an insertion indicator (in sense of 'inviting in').
'foreigner' becomes 'alien' (synonyms).
'st' placed around 'alien' is 'SALIENT'.
(Other definitions for salient that I've seen before include "Entails (anag) - most important" , "obvious" , "defence work" , "Prominent - in tales (anag)" , "Foremost" .)