Assumed Source database names:
Host: SUN1
Primary Database SID: PROD
Data file mount Point: /DB/PROD

Assuming Target Database:

Host: SUN2
Primary Database SID: CLONE
Data file mount Point: /DB/CLONE

Steps 1 Create init file for Clone instance

Set init parameter in init file.

DB_NAME=PROD to DB_NAME=CLONE
DB_FILE_NAME_CONVERT <----if using different mount point for database------->
LOG_FILE_NAME_CONVERT <----if using different mount point for database------>

Step 2 create Mount point for RMAN Backup set and Restore RMAN backup on Target Server

Note: RMAN backup set mount point must be same.

Step 3 Startup Clone Instance with Nomount option

Export ORACLE_SID=CLONE
Sqlplus /nolog
Conn / as sysdba
Startup nomount

Step 4 invoke RMAN

$ rman target sys/anup123@prod auxiliary /

Step 5 Execute bellow mention command on Rmount MAN prompt.

If database using same mount point:
RMAN> duplicate target database to “CLONE” nofilenamecheck;

If database using different mount point:

RMAN> duplicate target database to “CLONE” nofilenamecheck;