Departs city area in subtle desert transport (9)
I believe the answer is:
dromedary
'desert transport' is the definition.
(I've seen this before)
'departs city area in subtle' is the wordplay.
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'city' becomes 'rome' (Rome is an example).
'area' becomes 'a' (maths abbreviation).
'in' is an insertion indicator.
'subtle' becomes 'dry'.
'a' inserted into 'dry' is 'dary'.
'd'+'rome'+'dary'='DROMEDARY'
(Other definitions for dromedary that I've seen before include "Type of camel" , "Creature" , "Kind of camel" , "Animal" , "Arabian camel with one hump" .)