Maybe flat road north is blocked by hundreds of teeth (10)
I believe the answer is:
accidental
'maybe flat' is the definition.
(flat is a type of accidental note in music)
'road north is blocked by hundreds of teeth' is the wordplay.
'road north' becomes 'ai' (resembling Ac, road from London to Edinburgh).
'is blocked by' means one lot of letters goes inside another (I've seen this in other clues).
'hundreds' becomes 'cc' (I can't justify this - if you can you should believe this answer much more).
'of teeth' becomes 'dental' (I've seen this before).
'ai' enclosing 'cc' is 'acci'.
'acci'+'dental'='ACCIDENTAL'
Can you help me to learn more?
(Other definitions for accidental that I've seen before include "change of key" , "Happening by chance" , "Subsidiary" , "Unintended - sort of note" , "sign showing that flat may be got rid of?" .)