One young reporter employed by tabloid sent west is a nightmare (7)
I believe the answer is:
incubus
'nightmare' is the definition.
(synonyms)
'one young reporter employed by tabloid sent west' is the wordplay.
'one' becomes 'i' (Roman numeral).
'young reporter' becomes 'cub' (I've seen this in another clue).
'employed by' indicates putting letters inside (inserted letters used or employed inside).
'tabloid' becomes 'sun' (The Sun, UK newspaper).
'sent west' says the letters should be written in reverse (letters written left to right or 'east to west').
'sun' backwards is 'nus'.
'cub' placed within 'nus' is 'ncubus'.
'i'+'ncubus'='INCUBUS'
'is a' acts as a link.
(Other definitions for incubus that I've seen before include "Betraying Apostle" , "Burdensome person or evil spirit visiting sleeper" , "Nightmare - cub in us (anag)" , "Demon bringing nightmares" , "Male demon - nightmare - obsession" .)