Temporary effect of a false tooth (7)
'temporary' is the definition.
(a stopgap measure is a temporary one)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for stopgap that I've seen before include "Temporary measure", "Temporary fix", "A temporary or impromptu substitute", "A temporary substitute or solution", "Temporary expedient".)