Some discontent on gallant island nation (5)
I believe the answer is:
tonga
'island nation' is the definition.
(I've seen this before)
'some discontent on gallant' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'TONGA' can be found hidden inside 'discontent on gallant'.
(Other definitions for tonga that I've seen before include "part of Polynesia" , "The Friendly Islands" , "Two-wheeled Indian vehicle" , "group of Pacific islands" , "Horse-drawn vehicle" .)