Waste product containing salt (5)
I believe the answer is:
sweat
'salt' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'waste product' is the wordplay.
'waste' anagrams to 'SWEAT'.
Though, I am unsure how this is indicated.
'containing' acts as a link.
Can you help me to learn more?
(Other definitions for sweat that I've seen before include "Trouble in Australia" , "Salty fluid secreted by glands" , "Soldier" , "(Of argument) intense" , "Perspire" .)