Reveal end of world is nigh (8)
I believe the answer is:
disclose
'reveal' is the definition.
(disclosing is a kind of revealing)
'end of world is nigh' is the wordplay.
'end of' says to take the final letters.
'nigh' becomes 'close' ('close' can be similar in meaning to 'nigh').
The final letter of 'world' is 'd'.
'd'+'is'+'close'='DISCLOSE'
(Other definitions for disclose that I've seen before include "Make public" , "Divulge, reveal" , "Reveal, expose to view" , "Uncover" , "Betray" .)