Essential Tyneside editor gets flu treated (7)
I believe the answer is:
needful
'essential' is the definition.
(thesaurus)
'tyneside editor gets flu treated' is the wordplay.
'tyneside' becomes 'ne' (region in North East of England).
'editor' becomes 'ed'.
'gets' says to put letters next to each other.
'treated' indicates anagramming the letters.
'flu' is an anagram of 'ful'.
'ne'+'ed'+'ful'='NEEDFUL'
(Other definitions for needful that I've seen before include "Nude elf (anag.)" , "Required" , "Requisite, necessary" , "Poverty-stricken" , "poor" .)