Excessive, with no additional energy required to make the pace (4)
I believe the answer is:
step
'the pace' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
(Other definitions for step that I've seen before include "Pace - part of a procedure" , "Pace; foothold" , "Rung, dance movement" , "Set foot down on pest" , "one stage of flight" .)