Take court action before defence's case becomes material (5)
I believe the answer is:
suede
'material' is the definition.
(I've seen this before)
'take court action before defence's case' is the wordplay.
'take court action' becomes 'sue' (I've seen this before).
'before' says to put letters next to each other.
'case' says to hollow out the word (remove centre letters).
'defence' with its centre removed is 'de'.
'sue'+'de'='SUEDE'
'becomes' acts as a link.
(Other definitions for suede that I've seen before include "Soft leather with one side napped" , "Undressed leather" , "Fabric" , "leather material" , "Brushed leather" .)