Salt tablet with nail on top (8)
I believe the answer is:
pinnacle
'top' is the definition.
(I know that top can be written as pinnacle)
'salt tablet with nail' is the wordplay.
'salt' becomes 'nacl' (NaCl is the chemical formula for sodium chloride).
'tablet' becomes 'e' (E can mean ecstasy or an ecstasy tablet).
'with' says to put letters next to each other.
'nail' becomes 'pin' (both can mean a sharp object).
'nacl'+'e'='nacle'
'nacle' put after 'pin' is 'PINNACLE'.
'on' is the link.
(Other definitions for pinnacle that I've seen before include "Highest point of success" , "Place inn on the very top" , "The highest point, say of fame" , "Height of success" , "High pointed piece of rock" .)