Asian giant importing British energy (7)
I believe the answer is:
tibetan
'asian' is the definition.
(Tibet is in Asia)
'giant importing british energy' is the wordplay.
'giant' becomes 'titan' (titans are giant mythological creatures).
'importing' means one lot of letters goes inside another.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'energy' becomes 'e' (physics symbol as in E=mc2).
'b'+'e'='be'
'titan' going around 'be' is 'TIBETAN'.
(Other definitions for tibetan that I've seen before include "Asian" , "from high land" , "Former nationality of citizen of Lhasa" , "Nationality of citizen of Lhasa, before Chinese invasion" , "Nationality of the Dalai Lama" .)