What is the test for an insurance policy to be clear and unambiguous?

"An insurance policy, like any other contract, must be construed in its entirety, with each clause lending meaning to the other." Producers Dairy Delivery Co. v. Sentry Ins. Co., 41 Cal.3d 903, 718 P.2d 920, 928, 226 Cal.Rptr. 558 (1986) (internal quotation omitted). In determining whether a policy provision is clear and unambiguous, "words in an insurance policy must be read in their ordinary sense." Id. at 925. "A policy provision is ambiguous when it is capable of two or more constructions, both of which are reasonable." Id. at 924-25 (internal quotations omitted). "[A] finding of ambiguity in policy language cannot be based on an unreasonable misunderstanding on the part of the insured." Id. at 925. The existence of ambiguity is a question of law unless contract construction turns on the credibility of extrinsic evidence. Delgado v. Heritage Life Ins. Co., 157 Cal.App.3d 262, 203 Cal.Rptr. 672, 676 (1984). For Lira to be covered, Chicago's policy unambiguously requires that the act or omission creating exposure must result from the furnishing of professional rehabilitation services.