I searched over the web but all pages offers solutions via Photoshop. Is there a way to do it in lightroom or is PS the only solution? I'd think something like levels would help, but there are no levels in LR, or am I missing something?
I use an adjustment brush to paint the skin with clarity. "Clarity" is really "local contrast adjustment". If you search for tutorials using the latter keywords, you'll find several ways to do it in Photoshop. Be sure not to paint over blemishes or any other wrinkles that you don't want to emphasize.
There are two sets of basic curves in Lightroom (highlights, whites, shadows, blacks) and another one that can be R/G/B specific a bit further down that labels them differently (though I rarely use that one so I don't remember off the top of my head what they are called.)
There is also selective color boosts that could potentially be used to boost the particular colors associated with the freckles if they seem under saturated or possibly to alter the skin tone if it is detracting from the freckles.
Why do you think LR has no levels? It does and level curves gives you ability to change contrast as a function of brightness, which can help to bring out the aspect you need, but local contrast enhancement is usually what you need to make spots and lines pop out, while keeping the general brightness around the area. in LR that's called clarity. And you don't have to apply it over the entire image, you can brush it on.