Strange to send a line (5)
I believe the answer is:
alien
'strange' is the definition.
(synonyms)
'send a line' is the wordplay.
'send' is an anagram indicator (I've seen 'sends' mean this (send can mean excite or stir)).
'a'+'line'='aline'
'aline' with letters rearranged gives 'ALIEN'.
'to' acts as a link.
(Other definitions for alien that I've seen before include "Someone from outer space?" , "Not native" , "One is from outer space, perhaps" , "Belonging to a foreign country" , "of foreigners" .)