This may reproduce letters from clients (7)
I believe the answer is:
stencil
'this may reproduce letters' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'from clients' is the wordplay.
'from' is an anagram indicator (the anagram comes from the same letters).
'clients' is an anagram of 'STENCIL'.
Can you help me to learn more?
(Other definitions for stencil that I've seen before include "It helps get uniform print-out" , "Design inked through perforated sheet" , "Reproduction device for clients" , "Cut-out pattern for applying paint" , "outline" .)