But I still don't understand how clankles can apply to someone of very skinny proportions 
If somebody is so skinny that they have tiny skinny legs all the way up, then how can their ankles have much definition from their calves? Surely their ankles would then have to be thinner than an ankle bone could ever be?
I would have thought a 'clankle' can only apply when the whole leg isn't skinny? For example - if my ankles were no thinner than my calves - that would be a right clankley - clankle!