Indomitable courage - King George has it (4)
I believe the answer is:
grit
'indomitable courage' is the definition.
(I've seen this before)
'king george has it' is the wordplay.
'king george' becomes 'gr' (Georgius Rex).
'has' says to put letters next to each other.
'gr'+'it'='GRIT'
(Other definitions for grit that I've seen before include "Small loose particles of stone" , "Bottle" , "Grains of rock or sand" , "Small hard particles - determination" , "Toughness" .)