Country music's lead artist's opening act one (6)
I believe the answer is:
malawi
'country' is the definition.
(I know that Malawi is an country)
'music's lead artist's opening act one' is the wordplay.
'lead' suggests taking the first letters.
'opening' suggests taking the first letters.
'act' becomes 'law' (law is a kind of act).
'one' becomes 'i' (Roman numeral).
The initial letter of 'music' is 'm'.
The initial letter of 'artists' is 'a'.
'm'+'a'+'law'+'i'='MALAWI'
(Other definitions for malawi that I've seen before include "A law I'm making up in Southern Africa" , "It was Nyasaland under Britain" , "Former Nyasaland" , "Republic" , "Landlocked country of south central Africa" .)