How to Crochet a Cluster Stitch
A cluster (no abbreviation) is a set of crochet stitches that you work across an equal number of stitches and join together (or cluster) at the top, forming a triangle shape that resembles an upside-down shell stitch. Many crocheters use this stitch combination in conjunction with shells.
Yarn over (yo), insert the hook into the next stitch, yarn over, draw the yarn through the stitch, yarn over, draw the yarn through 2 loops on the hook.
Two loops remain on the hook. One half-closed double crochet is complete. A half-closed stitch is one that’s only worked partway, and then finished at the end of the combination.
Repeat the preceding step three times.
You should end up with 5 loops on the hook.
Yarn over and draw the yarn through all 5 loops on the hook
One 4-double-crochet (4-dc) cluster is complete.
Take a look at the symbol for a cluster stitch.
Many people who crochet prefer to read stitch diagrams instead of written instructions. This symbol for cluster stitch would appear in a crochet stitch diagram.