Your old-fashioned smithy suffers a 50 percent loss (3)
I believe the answer is:
thy
'your old-fashioned' is the definition.
(archaic word for 'your')
'smithy suffers a 50 percent loss' is the wordplay.
'THY' is hidden in amongst the letters.
But, I am uncertain how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for thy that I've seen before include "Belonging to thee" , "Your, of old" , "Your (archaic)" .)