Yarn in court before end of trial (4)
I believe the answer is:
wool
'yarn' is the definition.
(thesaurus)
'court before end of trial' is the wordplay.
'court' becomes 'woo' ('woo' can be a synonym of 'court'**).
'before' means one lot of letters go next to another.
'end of' suggests the final letters.
The last letter of 'trial' is 'l'.
'woo'+'l'='WOOL'
'in' is the link.
(Other definitions for wool that I've seen before include "Pull this over the eyes to deceive" , "Sheep's hair" , "Sheep's fleece" , "Fabric made from animal hair" , "Fleece of sheep" .)