SI unit spelt differently -- ampere in this country (7)
I believe the answer is:
tunisia
'in this country' is the definition.
(I've seen this before)
'si unit spelt differently ampere' is the wordplay.
'spelt differently' indicates an anagram.
'ampere' becomes 'a' (scientific unit).
'si'+'unit'='siunit'
'siunit' anagrammed gives 'tunisi'.
'tunisi'+'a'='TUNISIA'
(Other definitions for tunisia that I've seen before include "country-style" , "Land" , "African republic on the Mediterranean coast" , "North African republic" , "As Inuit visits there in North Africa" .)