Subtlety if turning head with energy (7)
I believe the answer is:
finesse
'subtlety' is the definition.
(I've seen this in another clue)
'if turning head with energy' is the wordplay.
'turning' says the letters should be written backwards.
'head' becomes 'ness' (ness is a headland).
'with' says to put letters next to each other.
'energy' becomes 'e' (physics symbol as in E=mce).
'if' backwards is 'fi'.
'fi'+'ness'+'e'='FINESSE'
(Other definitions for finesse that I've seen before include "Tact and poise in handling situations" , "Clever or crafty manoeuvring" , "Adroitness" , "Subtle skill - bridge manoeuvre" , "Sophistication" .)