Not necessarily. "Clone" means genetically identical. Identical twins are clones since they came from the same fertilized egg and have the same genome. However, identical twins are not genetically modified. Potatoes are clones. When they plant potatoes they put cut up potatoes in the ground instead of using seed. Therefore, it is the same plant regrowing. They are (natural) clones.
Genetically modified means that humans have inserted or removed DNA from the genome, or otherwise changed the DNA sequence. This can be a single gene or group of genes. You can insert that DNA into the parent stock, and the cross breed with other strains of that species. With cattle, you will get a mixture of genes in each offspring. With careful breeding and genetic screening you can select for offspring that are homozygous for the inserted DNA. That is, they carry the inserted DNA on each chromosome. However, they will be heterozygous in many other alleles, as will their offspring. They won't be clones, but they will be genetically modified.