Movement of foot initiating exercises? That's plain (6)
I believe the answer is:
steppe
'that's plain' is the definition.
(steppe is a kind of plain)
'movement of foot initiating exercises?' is the wordplay.
I cannot quite understand how this works, but
'movement' could be 'step' (step is a kind of movement) and 'step' is present in the answer.
'exercises?' could be 'pe' (Physical Education class) and 'pe' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for steppe that I've seen before include "Edxtensive plain" , "Dry grassy plain of eastern Europe and Asia" , "Large area of flat grassland in Europe or Siberia" , "plain territory" , "Flat area of eastern Europe or Russia" .)