Harsh, always, in London area (6)
I believe the answer is:
severe
'harsh' is the definition.
(thesaurus)
'always in london area' is the wordplay.
'always' becomes 'ever' ('ever' can be a synonym of 'always').
'in' is an insertion indicator.
'london area' becomes 'se' (abbreviation for South East).
'ever' inserted within 'se' is 'SEVERE'.
(Other definitions for severe that I've seen before include "Grave" , "Strait-laced" , "Taxing" , "Stern, austere" , "Arduous - dangerous" .)