The first to move with impact and energy (5)
I believe the answer is:
white
'the first to move' is the definition.
(white moves first in chess)
'with impact and energy' is the wordplay.
'with' becomes 'w' (short for with).
'impact' becomes 'hit' (hitting is a kind of impacting).
'and' means one lot of letters go next to another.
'energy' becomes 'e' (physics symbol as in E=mc2).
'w'+'hit'+'e'='WHITE'
(Other definitions for white that I've seen before include "Reflecting virtually all light" , "- Christmas, famous song" , "Colourless" , "Stainless" , "and 9: What Bing Crosby dreamed about" .)