Space Oddity 's backing singer's boring existence (6)
I believe the answer is:
entity
'existence' is the definition.
(I've seen this before)
'space oddity 's backing singer's boring' is the wordplay.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'oddity 's' becomes 'y' (I can't justify this - if you can you should believe this answer much more).
'backing' means one lot of letters go next to another.
'singer' becomes 'tit' (type of songbird).
'boring' is an insertion indicator (to bore something can mean to drill into it).
'en'+'y'='eny'
'eny' enclosing 'tit' is 'ENTITY'.
Can you help me to learn more?
(Other definitions for entity that I've seen before include "Object" , "Essence, existence" , "Individual being" , "Presence" , "It exists as a seperate thing (6)" .)