In there, you can find a source of oblivion (5)
I believe the answer is:
ether
'source of oblivion' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'in there you can find a' is the wordplay.
'there' can be anagrammed to 'ETHER'.
Though, I am unsure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for ether that I've seen before include "Old anaesthetic -- three (anag)" , "Rare atmosphere" , "There goes the anaesthetic" , "Some were put out by this" , "Former anaesthetic" .)