On finishing last, a complaint is just rubbish (5)
I believe the answer is:
trash
'just rubbish' is the definition.
'trash' can be an answer for 'rubbish' (I've seen this in another clue). I'm not certain of the 'just' bit.
'on finishing last a complaint' is the wordplay.
'on' is a charade indicator (letters next to each other).
'finishing' says to take the final letters (the letter which finishes the word).
'a complaint' becomes 'rash' (I've seen this before).
The final letter of 'last' is 't'.
't' put next to 'rash' is 'TRASH'.
'is' is the link.
Can you help me to learn more?
(Other definitions for trash that I've seen before include "pulp" , "bunk" , "Refuse; destroy" , "Worthless items" , "Dismiss as valueless" .)