Here camels roaming spit on one (4)
I believe the answer is:
gobi
'here camels roaming' is the definition.
The answer is a location as well as being a singular noun. This is suggested by the definition.
'spit on one' is the wordplay.
'spit on' becomes 'gob' (I can't explain this - if you can you should believe this answer much more).
'one' becomes 'i' (Roman numeral).
'gob'+'i'='GOBI'
Can you help me to learn more?
(Other definitions for gobi that I've seen before include "East Asian desert" , "The . . . . Desert is a barren plateau of S Mongolia and N China" , "Sandy area" , "arid area" , "Area of sand" .)