Basis for deciding a case (6)
I believe the answer is:
merits
'basis for deciding a case' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for merits that I've seen before include "Legally right or wrong" , "Deserves to be praised" , "Virtues of timers" , "Deserves, is worthy of" , "Deserves or warrants" .)