Marches, say, with marshal left in group (10)
I believe the answer is:
borderland
'marches' is the definition.
(I've seen this before)
'with marshal left in group' is the wordplay.
'with' means one lot of letters goes inside another.
'marshal' becomes 'order' (marshal can mean to order or gather).
'left' becomes 'l' (common abbreviation).
'in group' becomes 'band' (band can mean a group of people. I am not sure about the 'in' bit.).
'order'+'l'='orderl'
'orderl' placed within 'band' is 'BORDERLAND'.
'say' is the link.
Can you help me to learn more?
(Other definitions for borderland that I've seen before include "region close to frontier" , "marches" .)