We present observations of a coronal mass ejection (CME) associated with an eruptive prominence during 1998 June 21-22 by LASCO (Large Angle Spectroscopic Coronagraph) aboard SOHO (Solar and Heliospheric Observatory). Various features in the three-part structured, white-light CME as observed by LASCO-C2 and C3 coronagraphs were compared with features in the other wavelengths, for example, in Fe XIV and Fe X emission lines obtained from LASCO C1, in Hα from Helio-Research and at 17 GHz obtained from Nobeyama Radioheliograph. We have investigated conditions in several data sets to understand the eruptive and the pre-eruptive scenario of the CME. The CME and the eruptive prominence accelerate up to ~20 Rsolar and then decelerate to the velocity of the ambient slow solar wind. The analysis clearly shows that this particular CME is a typical case of a very slow or gradual CME for which it is difficult to define an exact onset time. The CME could be tracked for about 30 hours until it crossed a distance of 30 Rsolar and disappeared from the field of view of the LASCO-C3 coronagraph. The height-time profiles of various features of this CME suggest that the leading edge of the CME and the top of the prominence or the core follow similar pattern, implying a common driver for both the CME and the eruptive prominence. The observations provide strong evidence that the CME and the prominence eruption resulted from a common cause which is the global restructuring of the magnetic field in the corona in an extensive volume of space near and including the CME. The restructuring in turn was a consequence of newly emerging flux regions near and within the neighboring active regions close to the base of the CME.