All can be considered the same but 1 may cause confusion.
Bandwidth and circuit speed (in general sense) indicates the amount of bits that can be trasferred over a channel per second. But in Cisco terminology "bandwidth" command used under interface config is can be configured independent of the actual "circuit speed", it doesn't change the data rate it is used in metric calculations of some routing protocols (IGRP, EIGRP, OSPF in Cisco default) and some QoS configurations.
Clock rate is supplied to a DTE device by DCE and tells the DTE the circuit speed between DTE and DCE. So from DTE standpoint it is circuit speed.
Basic data rate of telecommunication systems is DS0 (64 Kbps) and comes from telephony standards: If you sample voice with 8KHz frequency and code each sample with 8 bits, you need 8 X 8= 64Kbps bandwidth to carry this digital signal. In telephony trunks each voice channel is 64Kbps and other faster channel types (T1, T3, E1, E3,) are comprised of DS0s.
Regards.
