Make sure the VLAN you want to have untagged on the port (in this example VLAN 203) is part of vlan-allowed and vlan-untagged. Then you set the actual untagged VLAN via pvid.

interface GigaEthernet0/2
 switchport trunk vlan-allowed 201,203,205
 switchport trunk vlan-untagged 203
 switchport mode trunk
 switchport pvid 203