The first person doing swirls in colour (6)
I believe the answer is:
indigo
'colour' is the definition.
(indigo is a kind of colour)
'the first person doing swirls in' is the wordplay.
'the first person' becomes 'i'.
'swirls' is an anagram indicator.
'in' indicates putting letters inside.
'doing' anagrammed gives 'indgo'.
'i' put into 'indgo' is 'INDIGO'.
(Other definitions for indigo that I've seen before include "One of the colours of the rainbow" , "Adulthood" , "Deep violet-blue colour" , "Blue-violet colour" , "Ellington's Mood" .)