Sandy is so courageous (6)
I believe the answer is:
gritty
This clue is a double definition.
'sandy' is the first definition.
('gritty' can be a synonym of 'sandy')
'so courageous' is the second definition.
'is' is the link.
(Other definitions for gritty that I've seen before include "Grimly realistic" , "Determined, plucky" , "Tough, uncompromising" , "Sandy" , "Hardy" .)