Like big dark space with a cover, sun being obscured (9)
I believe the answer is:
cavernous
'like big dark space' is the definition.
(like a cavern)
'a cover sun being obscured' is the wordplay.
'being obscured' indicates anagramming the letters (I've seen 'obscure' mean this).
'a'+'cover'+'sun'='acoversun'
'acoversun' with letters rearranged gives 'CAVERNOUS'.
'with' is the link.
(Other definitions for cavernous that I've seen before include "Roomy" , "Gaping" , "like a big pit" , "of large underground chambers" .)