Republican buy-out in stone (4)
I believe the answer is:
ruby
'stone' is the definition.
(I know that ruby is a type of transparent gem)
'republican buy-out in' is the wordplay.
'republican' becomes 'r' (political abbreviation).
'out' is an anagram indicator (out can mean wrong or inaccurate).
'in' means one lot of letters goes inside another.
'buy' anagrammed gives 'uby'.
'r' going within 'uby' is 'RUBY'.
(Other definitions for ruby that I've seen before include "Deep red - transparent gemstone" , "killed an assassin" , "Completely" , "Jack perhaps" , "Gemstone comprising mainly aluminium oxide" .)