Frustrates (5)
'frustrates' is the definition.
('foil' can be a synonym of 'frustrate')
This is the entire clue.
(Another definition for foils that I've seen is " Thwarts with kinds of swords".)
'frustrates' is the definition.
('thwart' can be a synonym of 'frustrate')
This is the entire clue.
(Other definitions for thwarts that I've seen before include "Blocks, prevents" , "Frustrates" .)