Room at the bottom of the sea or beyond the solar system (4,5)
I believe the answer is:
deep space
'sea or beyond the solar system' is the definition.
I can't tell whether this defines the answer.
'room at the bottom of' is the wordplay.
'room' becomes 'space' (I've seen this before).
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'the bottom of' becomes 'deep' (I can't explain this - if you can you should believe this answer much more).
'space' put after 'deep' is 'DEEP SPACE'.
'the' acts as a link.
Can you help me to learn more?
(Other definitions for deep space that I've seen before include "void" , "even devoid of 12 [THIN AIR]" , "Region beyond our atmosphere" .)