The Wichita consonant cluster alternations discussed here involve two opacity effects: the overapplication of affrication and the underapplication of cluster simplification. The stop /t/ affricates when followed by a consonant (e.g. /t + t/ --> [ct]). However, affrication appears to overapply even when the conditioning segment is absent in the output (e.g. /t + r/ --> [c]). In derivational terms, the consonant cluster appears to have undergone simplification after being affricated. Cluster simplification, however, underapplies if the affricate is an underlying affricate (e.g. /c +s/ --> [cs]). In this paper, I first suggest that the affrication in Wichita be best analyzed as a case of coalescence, and propose that the affrication follows from a positional markedness constraint defined in terms of the syllable (Zoll 1998). Furthermore, I argue that the markedness constraint is reducible to a more general condition on sonority. In order to account for the nonderived environment blocking effect, I also propose a locally conjoined constraint (LC) à la Lubowicz (1998) where a markedness constraint and an Input-Output faithfulness constraint (IO-faithfulness) are conjoined. Since the LC can be violated only when the IO-faithfulness is violated (i.e., in derived environments), the cluster reduction is effectively blocked only in non-derived environments.