Copper say seen in gruesome tale (5)
I believe the answer is:
metal
'copper say' is the definition.
(I know that Cu is a type of metal)
'in gruesome tale' is the wordplay.
'in' indicates a hidden word.
'METAL' can be found hidden inside 'gruesome tale'.
'seen' acts as a link.
(Other definitions for metal that I've seen before include "employed in making roads" , "Alloy" , "Zirconium, for example" , "Tungsten, for example" , "Broken stones" .)