Test regularly applied for instance (7)
I believe the answer is:
example
'instance' is the definition.
(I know that instance can be written as example)
'test regularly applied' is the wordplay.
'test' becomes 'exam' (synonyms).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'applied' are 'ple'.
'exam'+'ple'='EXAMPLE'
'for' acts as a link.
(Other definitions for example that I've seen before include "Characteristic item" , "Something illustrating a general rule" , "Thing characteristic of its kind" , "Illustration or paradigm" , "Specimen, sample" .)