Place swathed in unadulterated colour (6)
I believe the answer is:
purple
'colour' is the definition.
(I know that purple is a more specific form of the action colour)
'place swathed in unadulterated' is the wordplay.
'place' becomes 'pl' (abbreviation used in postal addresses).
'swathed in' is an insertion indicator (swathe can mean to wrap).
'unadulterated' becomes 'pure' (similar in meaning).
'pl' inserted inside 'pure' is 'PURPLE'.
(Other definitions for purple that I've seen before include "shade" , "Mixture of red and blue" , "Colour obtained from mixing red with blue" , "Red and blue mix" , "Red and blue mixed" .)