Smile as unsettling as unsettled (7)
I believe the answer is:
aimless
'unsettled' is the definition.
(similar in meaning)
'smile as unsettling' is the wordplay.
'unsettling' is an anagram indicator.
'smile'+'as'='smileas'
'smileas' is an anagram of 'AIMLESS'.
'as' acts as a link.
(Other definitions for aimless that I've seen before include "Without purpose or direction" , "not knowing where to go?" , "Lacking a goal" , "Without purpose, like Melissa" , "Without purpose or target" .)