Section of foot soldiers marching must be this (6)
I believe the answer is:
instep
'section of foot' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for instep that I've seen before include "Part of foot under spinet" , "Central part of a foot" , "Arch area of the foot" , "One part of Oxford" , "Part of foot between toes and ankle" .)