Sovereign's deputy (7)
I believe the answer is:
viceroy
'sovereign's deputy' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for viceroy that I've seen before include "sovereign's governor" , "Monarch's plenipotentiary - American butterfly, like (but smaller than) a monarch" , "Governor ruling in name of sovereign" , "Sovereign's representative in a colony" , "One ruling in a colony" .)