Old relative sheds pound in weight (5)
I believe the answer is:
ounce
This clue might be a double definition.
'old relative sheds pound' is the first definition.
'ounce' can be an answer for 'pound' (thesaurus). I am not sure about the 'old relative sheds' bit.
'weight' is the second definition.
(I know that ounce is a type of troy unit)
'in' is the link.
Can you help me to learn more?
(Other definitions for ounce that I've seen before include "Large cat" , "Wildcat" , "A little bit" , "one of a number in the pound" , "Small quantity - weight" .)