Documentation for JIRA 4.2. Documentation for other versions of JIRA is available too.

ClearCase is supported by Atlassian FishEye, providing comprehensive integration with JIRA including real-time notifications of code changes plus web-based reporting, visualisation, search and code sharing. For details, please see Integrating JIRA with FishEye.

Alternatively, there is a JIRA ClearCase plugin which shows ClearCase checkins associated with JIRA issues. Please note that this plugin is not developed or supported by Atlassian.