Pass over vast areas creating disorder (7)
I believe the answer is:
disease
'disorder' is the definition.
(I have seen 'Bodily disorder ' mean 'disease' so perhaps 'disorder' could also mean 'disease')
'pass over vast areas' is the wordplay.
'pass' becomes 'ID' (identification).
'over' shows that the letters should be reversed in order.
'vast areas' becomes 'sease' (I can't justify this - if you can you should believe this answer much more).
'id' in reverse letter order is 'di'.
'di'+'sease'='DISEASE'
'creating' is the link.
Can you help me to learn more?
(Other definitions for disease that I've seen before include "scurvy?" , "Bodily disorder" , "Impairment of health" , "Seaside (anag) -- ailment" , "Sickness" .)