Great distance, around 100 kilometres (6)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

MILE (distance) containing [around] C (100) + K (kilometres). I knew this word only from the saying Many a mickle makes a muckle but didn’t even know what that meant. The dictionaries confirm ‘muckle’ means ‘great’ or as a noun ‘a great amount’ but Collins confuses the issue by adding that in Scotland ‘muckle’ means a small amount. I quote verbatim the entry in Brewer’s which perhaps explains all: the original Scottish proverb is A wheen o’mickles mak’s a muckle, where mickle means ‘little’ and muckle ‘much’. However micel or mycel means ‘much’, so that if the Scots proverb is accepted, a converse meaning must be given to mickle.