The mere result of frost is only fair (7)
I believe the answer is:
justice
'only fair' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'the mere result of frost' is the wordplay.
'the mere result of' becomes 'just' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'frost' becomes 'ice' (synonyms).
'just'+'ice'='JUSTICE'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for justice that I've seen before include "Fairness, legitimacy" , "Magistrate's title" , "Courts' function" , "Judge, magistrate" , "amends" .)