Shake foundation (4)
I believe the answer is:
rock
I believe this clue is a double definition.
'shake' is the first definition.
('rock' can be a synonym of 'shake')
'foundation' is the second definition.
(thesaurus)
(Other definitions for rock that I've seen before include "Seaside confectionery" , "Big stone - music" , "Sweet < music" , "Reel from" , "to soothe baby" .)