The Collaborative International Dictionary of English v.0.48:

Clearstarch \Clear"starch`\ (kl[=e]r"st[aum]rcht`), v. t. [imp.
   & p. p. Clearstarched; p. pr. & vb. n. Clearstraching.]
   To stiffen with starch, and then make clear by clapping with
   the hands; as, to clearstarch muslin.
   [1913 Webster]