Aha - yet another Parts of the Body idiom. The issue 'at hand' is the issue uppermost in the minds of all the relevant people. For example, at a business meeting the 'issue at hand' would be fairly high on the agenda. Don't confuse 'at hand' with the idiomatic usage 'to hand' - within easy reach: "I think I'm free at that time, but I don't have my diary to hand".
(I wonder whether I thought of that example because I was wondering whether I should have used 'agenda' in my first example. This is a false friend: 'agenda' doesn't mean 'diary'; 'an agenda' is a list of things to be discussed. The word 'agenda' is also used figuratively to mean 'something that can be discussed': "Don't mention our previous relationship: that's just not on the agenda".)