Depression is over on entering bar (5)
I believe the answer is:
basin
'depression' is the definition.
(basin is a kind of depression)
'is over on entering bar' is the wordplay.
'over' indicates an anagram.
'on entering' is an insertion indicator.
'bar' becomes 'ban' (bar can mean to ban or prohibit).
'is' anagrammed gives 'si'.
'si' put inside 'ban' is 'BASIN'.
(Other definitions for basin that I've seen before include "Water receptacle" , "Round open dish for washing" , "Region drained by a river" , "container" , "Washbowl" .)