Entering Belgium, a liberated country (4)
I believe the answer is:
mali
'country' is the definition.
(Mali is an example)
'entering belgium a liberated' is the wordplay.
'entering' says the answer is hidden in the clue.
'MALI' is hidden within 'belgium a liberated'.
(Other definitions for mali that I've seen before include "Timbuktu is in this landlocked country" , "Send mail out to Africa" , "African country, former French colony" , "part of Africa" , "Indian gardener; African republic" .)