Inedible bit of fish discarded after I washed up (8)
I believe the answer is:
finished
'washed up' is the definition.
(thesaurus)
'inedible bit of fish discarded after i' is the wordplay.
'inedible bit of fish' becomes 'fin' (I can't justify this - if you can you should believe this answer much more).
'discarded' becomes 'shed' (I've seen this before).
'after' is a charade indicator (letters next to each other).
'shed' put after 'i' is 'ished'.
'fin'+'ished'='FINISHED'
Can you help me to learn more?
(Other definitions for finished that I've seen before include "exhausted" , "Ended. completed" , "wrapped up" , "dressed" , "Complete" .)