So-called president died — like this, not in theatre (4)
I believe the answer is:
abed
'this not in theatre' is the definition.
The definition suggests a singular noun but the answer is not.
'so-called president died' is the wordplay.
'so-called president' becomes 'abe' (Abraham (Abe) Lincoln. I am not sure about the 'so-called' bit.).
'died' becomes 'd' (abbreviation next to the year of someone's death).
'abe'+'d'='ABED'
'like' acts as a link.
Can you help me to learn more?
(Other definitions for abed that I've seen before include "going to sleep?" , "Sleeping under covers" , "not exactly stirring" , "Retired for the night" , "Having not got up" .)