Exercise follows walk in smooth flat land (6)
I believe the answer is:
steppe
'smooth flat land' is the definition.
'steppe' can be an answer for 'land' (steppe is a kind of land). I also know that 'flat' relates to this answer.
'exercise follows walk' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'follows' says to put letters next to each other.
'walk' becomes 'step' (I've seen this before).
'pe' put after 'step' is 'STEPPE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for steppe that I've seen before include "Edxtensive plain" , "Dry plain of Eurasia" , "(Russian) grassy plain" , "Dry grassy plain of central Europe" , "Dry grassy plain of eastern Europe and Asia" .)