Newspaper printed upside-down? All right, it's the end of the world! (8)

'the end of the world' is the definition.
(Ragnarok is the end of the world in Norse myth)

'newspaper printed upside-down? all right' is the wordplay.
'newspaper' becomes 'rag' (informal term for a newspaper).
'printed' becomes 'ran' (running is a kind of printing).
'upside down?' is a reversal indicator (I've seen 'upside down' mean this).
'all right' becomes 'ok' (synonyms).
'ran' in reverse letter order is 'nar'.
'rag'+'nar'+'ok'='RAGNAROK'

'it's' is the link.