K, on the periodic table (9)
I believe the answer is:
potassium
'k on the periodic table' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for potassium that I've seen before include "Soft metallic element" , "... is its atomic number: symbol K" , "Element K" , "Soft reactive metal" , "Soft metal, symbol K" .)