Energy at the back from one direction (7)
I believe the answer is:
eastern
'one direction' is the definition.
(I've seen this before)
'energy at the back' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'at the back' becomes 'astern' (I've seen this before).
'e'+'astern'='EASTERN'
'from' acts as a link.
(Other definitions for eastern that I've seen before include "from afar" , "Maybe Chinese" , "See 11" , "Earnest (anag.)" , "in Beijing, possibly" .)