Cut terribly crude energy (6)
I believe the answer is:
reduce
'cut' is the definition.
(I know that cut is a action)
'terribly crude energy' is the wordplay.
'terribly' is an anagram indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'crude' is an anagram of 'reduc'.
'reduc'+'e'='REDUCE'
(Other definitions for reduce that I've seen before include "diet" , "Boil down or cut back" , "Diminish" , "Of a sauce, thicken" , "Shrink" .)