Country, one hit hard in revolution (4)
I believe the answer is:
mali
'country' is the definition.
(Mali is an example)
'one hit hard in revolution' is the wordplay.
'one' becomes 'i' (Roman numeral).
'hit hard' becomes 'lam' (to 'lam' means to hit hard**).
'in revolution' says the letters should be written backwards.
'i'+'lam'='ilam'
'ilam' reversed gives 'MALI'.
(Other definitions for mali that I've seen before include "African country, former French colony" , "Timbuktu is in this landlocked country" , "African country, once French Sudan" , "Send mail out to Africa" , "African state's" .)