Start to show to advantage (3,3)
I believe the answer is:
set off
I believe this is a double definition.
'start' is the first definition.
(I know that start can be written as set off)
'show to advantage' is the second definition.
(I've seen this before)
'to' is the link.
(Other definitions for set off that I've seen before include "Depart" , "Begin journey or cause to ignite" , "radio with no reception" , "Display - mount - start journey" , "show to advantage" .)