Like ring topped with cool blue (6)
I believe the answer is:
indigo
'blue' is the definition.
(I know that indigo is a type of blue)
'like ring topped with cool' is the wordplay.
'like' becomes 'dig' (to dig can mean to appreciate or 'get').
'ring' becomes 'O' (O is the shape of a ring).
'topped with' says to put letters next to each other.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'dig'+'o'='digo'
'digo' put after 'in' is 'INDIGO'.
(Other definitions for indigo that I've seen before include "Mood - (Duke Ellington)" , "A deep blue dye or colour" , "Natural blue dye" , "Violet-blue dye" , "product of woad" .)