A mews working around zero energy is stunning (7)
I believe the answer is:
awesome
'is stunning' is the definition.
(I've seen this in another clue)
'a mews working around zero energy' is the wordplay.
'working' indicates anagramming the letters.
'around' is an insertion indicator.
'zero' becomes 'O' (O resembles 0).
'energy' becomes 'e' (physics symbol as in E=mc2).
'mews' anagrammed gives 'wesm'.
'wesm' going around 'o' is 'wesom'.
'a'+'wesom'+'e'='AWESOME'
(Other definitions for awesome that I've seen before include "staggering" , "Exceptionally good" , "Inspiring fear/wonder" , "Magnificent, causing fear or wonder" , "Frightening but impressive" .)