Departs one precise area (8)
I believe the answer is:
district
'area' is the definition.
(I know that area can be written as district)
'departs one precise' is the wordplay.
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'one' becomes 'i' (Roman numeral).
'precise' becomes 'strict' (I've seen this before).
'd'+'i'+'strict'='DISTRICT'
(Other definitions for district that I've seen before include "Territory, zone" , "London Underground line represented in green" , "Locality" , "Zone, area" , "Precinct, section" .)