Pointless trial attorney has abandoned before end of day (5)
I believe the answer is:
empty
'pointless' is the definition.
(thesaurus)
'trial attorney has abandoned before end of day' is the wordplay.
'trial' becomes 'attempt'.
'attorney' becomes 'att' (abbreviation for attorney).
'has abandoned' is a deletion indicator.
'before end of day' becomes 'y' (I can't justify this - if you can you should believe this answer much more).
'attempt' with 'att' taken away is 'empt'.
'empt'+'y'='EMPTY'
(Other definitions for empty that I've seen before include "Void; vacant" , "'. . . . . vessels make the most sound'" , "worthless" , "Loneliness parents feel when their children leave home" , "Cleared out" .)