Closest are sent away (7)
I believe the answer is:
nearest
'closest' is the definition.
('nearest' can be a synonym of 'closest')
'are sent away' is the wordplay.
'away' is an anagram indicator.
'are'+'sent'='aresent'
'aresent' with letters rearranged gives 'NEAREST'.
(Other definitions for nearest that I've seen before include "Next" , "Relations" , "Closest among relatives" , "Most adjacent" , "Most accessible" .)