Twice self-employed in cultural unit (4)
I believe the answer is:
meme
'twice self-employed in cultural unit' is the definition.
The definition suggests a singular noun which matches the answer.
'in cultural unit' is the wordplay.
'in' is an insertion indicator.
'cultural' becomes 'me' (I can't justify this - if you can you should believe this answer much more).
'unit' becomes 'em' (em is a kind of unit).
'me' enclosing 'em' is 'MEME'.
Can you help me to learn more?
(Other definitions for meme that I've seen before include "Often trite image" , "Concept that spreads rapidly on the Internet" , "Cultural belief that assumes a life of its own" , "Behavioural trait" , "Question that spreads on the internet" .)