Shell small to medium-sized, claviform, with high orthoconoid spire and rather gentle sculpture. Protoconch paucispiral, of about 1.5-1.75 smooth white whorls. Teleoconch of about 8 whorls; suture deeply impressed but not canaliculate. Early teleoconch whorls with blunt angulation at about mid-height; later whorls with steep slightly concave subsutural ramp changing to a rounded shoulder at about mid-height of whorl. Sculpture of regular, rounded axial folds (14 on last whorl, 12 on penultimate whorl), more weakly pronounced on subsutural ramp, stronger on shoulder and on whorl periphery. On last adult whorl subsutural ramp separated from lower portion of whorl by a distinct, although rather wide, groove. Microsculpture of very fine, vanishing collabral growth lines, intersected by dense, also very fine, grooves in the interspaces between axials. Shell base with somewhat truncated appearance; siphonal canal short and robust, widely open, with well-developed fasciole.
Aperture ovate; outer lip with distinct stromboid notch in its anterior part, irregularly denticulate within. Anal sinus rather deep, U-shaped, constricted by a callous pad at posterior apertural corner. Inner lip with well-developed pale callus. Shell uniformly tan to sometimes lighter subsutural ramp, shell base and crests of axial folds, periphery of whorls darker, interspaces between axials light brown.

Although showing close affinity to Clavus exasperatus, Clavus kirkhammetti n. sp. is different to the former, as well as other species of the analysed complex, in having a more elongated shell with lower and more numerous nodules at the shoulder extended into rounded folds, and by its comparatively much shallower suture. As well, the species can be readily identified by its colouration, lacking a contrasting band on the shell periphery, and sometimes showing an almost uniformly tan shell.
It should be noted that conchologically, Clavus kirkhammetti n. sp. cannot be attributed to the C. canalicularis species complex, and the position of this species in the tree (as a sister to C exasperatus) rejects the monophyly of the Clavus canalicularis complex. Further studies with broader taxon sampling are needed to shed light on the relationships of the forms analysed herein within Clavus, as well as to establish limits between the genera Clavus, Drillia Gray, 1838 and Tylotiella Habe, 1958.

Off South Madagascar, shallow subtidal depths.