If find yourself clearing your throat a lot, and you don't have a history of allergies, and you're not recovering from a cold, it could be a symptom of acid reflux. Most people associate acid reflux with symptoms of heart burn, but you could actually have laryngopharyngeal reflux, or LPR. This happens when small amounts of acid escape into the esophagus and splash down the windpipe, or pharynx, which causes tissue injury--especially to the voicebox, or larynx. Doctors say that less than 14% of patients with LPR experience heartburn. However, this is still a serious condition, and you should see a doctor.
Aside from frequent throat clearing, other symptoms of laryngopharyngeal reflux can include hoarseness, chronic cough, asthma (especially if you didn't have childhood asthma), tenderness in the voicebox region, and changes in the voice.
Source: "Clearing of Throat; Acid Reflux Linked"