Old and harshly uninviting smell (5)
I believe the answer is:
odour
'smell' is the definition.
('odour' can be a synonym of 'smell')
'old and harshly uninviting' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'and' is a charade indicator (letters next to each other).
'harshly uninviting' becomes 'dour'.
'o'+'dour'='ODOUR'
(Other definitions for odour that I've seen before include "Distinctive smell" , "Stench" , "Aroma or fragrance" , "Perfume" , "for the nose to detect" .)