They may measure a diamond ring as it's reset (6)
I believe the answer is:
grains
'they may measure a diamond' is the definition.
The definition suggests an adverb but the answer is not.
'ring as it's reset' is the wordplay.
'it's reset' indicates anagramming the letters.
'ring'+'as'='ringas'
'ringas' anagrammed gives 'GRAINS'.
Can you help me to learn more?
(Other definitions for grains that I've seen before include "Granular particles" , "Seeds" , "Tiny pieces of wheat or sand" , "Particles of sand" , "'Granules, kernels (6)'" .)