Can anxiety lead to excessive mucus in the throat and/or throat clearing?

Not really: As anxiety is more known to "dry" the mouth making speaking difficult. On the other hand, in your case, anxiety may trigger a reflexive "clearing" throat irritating the pharynx enough to produce excessive mucous. An allergic reaction and/or viral infection should be ruled out. Get your gp have your throat examined first & then see a mental health professional 2 get help w/ your anxiety.