Sell coats round old back street in March with difficulty (8)
I believe the answer is:
footslog
'march with difficulty' is the definition.
'footslog' can be an answer for 'march' (I've seen this before). I am not sure about the 'with difficulty' bit.
'sell coats round old back street' is the wordplay.
'sell' becomes 'flog' (I've seen this before).
'coats' means one lot of letters goes inside another (inserted letters are coated in another word).
'round' becomes 'o' (o is a circular letter).
'old back street' becomes 'ots' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'o'+'ots'='oots'
'flog' enclosing 'oots' is 'FOOTSLOG'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for footslog that I've seen before include "Long and exhausting march" , "Tramp" , "what soldier does" , "arduous journey" , "exhausting hike" .)