Ask for an out. Explain that it's how you keep your skills up to date, and that it lets you be a more productive and effective employee. In the past I've had this clause in my contracts and had them take it out. They did.
In one case, an international company with a couple-thousand employees in the US, the company lawyers never got back to me, but the next year the contract was changed and it included a variation of my original proposed language. In the other case, a US company with tens of thousands of employees, the company lawyers got back to me immediately with a statement about how they intended the existing language to be interpreted (and this addressed my concerns).
I can't promise you will get the same results, but I thought it was worth sharing my anecdotes.