I just logged in to webmaster tools and saw those figures for a keyword I am ranking top rated for.

Impressions: 3500, Clicks 300.

I am definitely ranking leading for this keyword (I have checked a number of times).

A one0% CTR at occupation one in the SERPS is abysmal. DO you think its possible or could there be a mistake in webmaster instruments?

may well it be down to a bad meta description? Surely a lot more than one0% of individuals would blindly click the top rated result without reading it anyway?