Neil upset band (4)
I believe the answer is:
line
'band' is the definition.
(thesaurus)
'neil upset' is the wordplay.
'upset' is an anagram indicator.
'neil' with letters rearranged gives 'LINE'.
(Other definitions for line that I've seen before include "Long mark; direction" , "Formation of one beside another" , "Row - occupation" , "column" , "Row; track" .)