Screen regularly to exclude rejected currency (7)
I believe the answer is:
centimo
'currency' is the definition.
(currency unit in several Latin American countries)
'screen regularly to exclude rejected' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'to exclude' becomes 'omit' (synonyms).
'rejected' says the letters should be written backwards.
The alternate letters of 'screen' are 'cen'.
'omit' backwards is 'timo'.
'cen'+'timo'='CENTIMO'
(Other definitions for centimo that I've seen before include "money abroad" , "smallest in Peru" , "Small coin of some S. American countries" , "very little money" , "Monetary unit of some Spanish-speaking countries" .)