Stencil designed for customers (7)
I believe the answer is:
'for customers' is the definition.
('client' can be a synonym of 'customer')
'stencil designed' is the wordplay.
'designed' is an anagram indicator (designed with the letters).
'stencil' is an anagram of 'CLIENTS'.
(Other definitions for clients that I've seen before include "Stencil (anag)" , "Consumers" , "Customers of the professions" .)