Show fellow setter heartless editorials in newspaper (8)
I believe the answer is:
manifest
'show' is the definition.
(manifesting is a kind of showing)
'fellow setter heartless editorials in newspaper' is the wordplay.
'fellow' becomes 'man' (I've seen this before).
'setter' becomes 'i' (the person that set the crossword).
'heartless' says to hollow out the word (remove centre letters).
'in' means one lot of letters goes inside another.
'newspaper' becomes 'ft' (Financial Times newspaper).
'editorials' with its middle taken out is 'es'.
'es' put into 'ft' is 'fest'.
'man'+'i'+'fest'='MANIFEST'
(Other definitions for manifest that I've seen before include "List of a ship's contents" , "Display" , "Easily noticed - cargo list" , "List of ship's cargo or passengers" , "(Of ghost) appear" .)