Speed and power in exercises (4)
I believe the answer is:
pace
'speed' is the definition.
(pace is a kind of speed)
'power in exercises' is the wordplay.
'power' becomes 'AC' (AC is an example).
'in' indicates putting letters inside.
'exercises' becomes 'pe' (Physical Education class).
'ac' going inside 'pe' is 'PACE'.
'and' is the link.
(Other definitions for pace that I've seen before include "Tempo, rate of moving" , "Speed of walking" , "With due respect" , "Rate of progress" , "Step or tempo" .)