Writer making copper three dimensional (5)
I believe the answer is:
cubic
'dimensional' is the definition.
(thesaurus)
'writer making copper three' is the wordplay.
I cannot really see how this works, but
'writer' could be 'bic' (kind of pen) and 'bic' is found within the answer.
'copper' could be 'cu' (chemical symbol) and 'cu' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for cubic that I've seen before include "Having three dimensions" , "Like sugar lumps" , "The first C in cc" , "(Of a solid) square-sided" , "As volumetric measures" .)