Thick ring, black and teal on top has value (6)
I believe the answer is:
obtuse
'thick' is the definition.
(I've seen this before)
'ring black and teal on top has value' is the wordplay.
'ring' becomes 'o'.
'black' becomes 'b' (as in pencil classifications).
'and' is a charade indicator (letters next to each other).
'on top' says to take the initial letters.
'has value' becomes 'use' (I can't justify this - if you can you should give a lot more credence to this answer).
The first letter of 'teal' is 't'.
'o'+'b'+'t'+'use'='OBTUSE'
Can you help me to learn more?
(Other definitions for obtuse that I've seen before include "Annoyingly insensitive" , "angle, perhaps" , "Dopey" , "(Of angle) between 90deg and 180deg - dull" , "Blunt - stupid - insensitive" .)