Tarnish on coin has dissolved in spirit (10)
I believe the answer is:
maraschino
'spirit' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'tarnish on coin has dissolved' is the wordplay.
'tarnish' becomes 'mar' (I've seen this in another clue).
'on' says to put letters next to each other.
'dissolved' is an anagram indicator.
'coin'+'has'='coinhas'
'coinhas' is an anagram of 'aschino'.
'mar'+'aschino'='MARASCHINO'
'in' acts as a link.
Can you help me to learn more?
(Another definition for maraschino that I've seen is " Harmonicas (anag) - cherry liqueur".)