Cheers! A double feature! (4-4)
I believe the answer is:
chin-chin
'cheers' is the definition.
(I've seen this before)
'a double feature' is the wordplay.
'a double' shows that letters should be duplicated.
'feature' becomes 'chin' (facial feature).
'chin' duplicated is 'CHIN-CHIN'.
(Other definitions for chin-chin that I've seen before include "Down the hatch!" , "Cheers, bottoms up" , "good health ..." .)