A dateline otherwise set apart (9)
I believe the answer is:
alienated
'apart' is the definition.
(thesaurus)
'a dateline otherwise' is the wordplay.
'otherwise' indicates anagramming the letters.
'dateline' with letters rearranged gives 'lienated'.
'a'+'lienated'='ALIENATED'
'set' acts as a link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for alienated that I've seen before include "disaffected" , "Estranged" , "divorced" , "put off" , "Date Liane (anag.)" .)