Cardinal may see fortune wasted taking drug (8)
I believe the answer is:
fourteen
'cardinal' is the definition.
(I know that fourteen is a stella octangula number)
'fortune wasted taking drug' is the wordplay.
'wasted' indicates an anagram.
'taking' is an insertion indicator.
'drug' becomes 'e' (E is another name for ecstasy).
'fortune' anagrammed gives 'fourten'.
'fourten' enclosing 'e' is 'FOURTEEN'.
'may see' acts as a link.
(Other definitions for fourteen that I've seen before include "Number of lines in a sonnet" , "Pounds in a stone?" , "XIV" , "Fen route (anag)" .)