Winter wind removes one from invalid court case (7)
I believe the answer is:
mistral
'winter wind removes' is the definition.
I know that 'wind' relates to this answer. I also know that both the answer and definition are singular nouns
'one from invalid court case' is the wordplay.
'one from invalid' becomes 'mis' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'court' becomes 'trial court' (trial court is a kind of court).
'case' means to remove the middle letters.
'trial' with its centre removed is 'tral'.
'mis'+'tral'='MISTRAL'
Can you help me to learn more?
(Other definitions for mistral that I've seen before include "That's a blow" , "Cold dry wind in southern France" , "Nice chiller" , "A harsh blow" , "Strong cold dry wind" .)