Radios covering end of nasty dictatorships (9)

'dictatorships' is the definition.
('tyranny' can be a synonym of 'dictatorship')

'radios covering end of nasty' is the wordplay.
'radios' becomes 'trannies' (short for transistor radios).
'covering' means one lot of letters goes inside another.
'end of' says to take the final letters.
The last letter of 'nasty' is 'y'.
'trannies' going around 'y' is 'TYRANNIES'.