Altered ground on which you might step (7)
I believe the answer is:
treadle
'which you might step' is the definition.
I can't tell whether this definition defines the answer.
'altered ground' is the wordplay.
'ground' indicates an anagram ('grind' the letters into a new form).
'altered' is an anagram of 'TREADLE'.
'on' is the link.
Can you help me to learn more?
(Other definitions for treadle that I've seen before include "Foot lever giving power" , "Foot pedal for power" , "driving mechanism" , "requires footwork" , "Machine foot-lever" .)