Go from first to second to suspend energy on entering knockout competition? (6,2)
I believe the answer is:
change up
'go from first to second' is the definition.
(as in changing gear in a vehicle)
'suspend energy on entering knockout competition?' is the wordplay.
'suspend' becomes 'hang' (I've seen this before).
'energy' becomes 'e' (physics symbol as in E=mc2).
'on' means one lot of letters go next to another.
'entering' is an insertion indicator.
'knockout competition?' becomes 'cup'.
'hang'+'e'='hange'
'hange' put within 'cup' is 'CHANGE-UP'.
'to' acts as a link.
(Another definition for change up that I've seen is " Engage higher gear".)