A baby with a short frenulum can "click" or "chuck" when the tongue "snaps back." The tongue is unable to extend itself for the *prolonged* job of keeping the nipple compressed up against the hard palate, in order to effectively remove milk from the breast. Because of the negative pressure going on inside the mouth (all that suction power!), the tongue snaps back should the "grip" fail.
"Tongue suckers" sometimes click. Such a baby is accustomed to the sensation of her own tongue up against the roof of her mouth. Baby may close and latch-on too quickly: as soon as she senses something entering her mouth. If Mom's nipple and breast aren't fully extended into the mouth cavity, there is an air space in the mouth. Clicking can result as baby sucks on that air space. You'll often see cheek dimpling when this sort of clicking is going on.
Clicking can also result if baby cannot get the nipple/breast fully into the mouth, and compressed against the roof of the mouth, due to unusual anatomical variations: highly-arched roof; perhaps a cleft of the soft palate; unusually small or large tongue, etc. etc.
Liz Brooks, JD, IBCLC