Current victory in legal case is worthless (7)
I believe the answer is:
trivial
'worthless' is the definition.
(thesaurus)
'current victory in legal case' is the wordplay.
'current' becomes 'i' (symbol for electric current).
'victory' becomes 'v'.
'in' means one lot of letters goes inside another.
'legal case' becomes 'trial' (I've seen this before).
'i'+'v'='iv'
'iv' inserted into 'trial' is 'TRIVIAL'.
'is' acts as a link.
(Other definitions for trivial that I've seen before include "Slight" , "Piddling" , "Quite unimportant and paltry" , "Trifling" , "Very easy" .)