A down-to-earth passage (7)
I believe the answer is:
landing
'a down-to-earth passage' is the definition.
'landing' can be an answer for 'passage' (I have seen 'Upstairs passage ' mean 'landing' so perhaps 'passage' could also mean 'landing'). I'm not certain of the 'a down-to-earth' bit.
'earth passage' is the wordplay.
'earth' becomes 'land' (synonyms).
'passage' becomes 'ing' (I can't explain this - if you can you should believe this answer much more).
'land'+'ing'='LANDING'
Can you help me to learn more?
(Other definitions for landing that I've seen before include "Reaching the shore" , "Upstairs passage" , "Going ashore at the top of the stairs" , "End of a flight" , "Top of a staircase" .)