Mystical old characters smuggle illegal drugs (5)
I believe the answer is:
runes
'mystical old characters' is the definition.
'runes' can be an answer for 'characters' (rune is a kind of character). I am unsure of the 'mystical old' bit.
'smuggle illegal drugs' is the wordplay.
'smuggle' becomes 'run' (I've seen this in another clue).
'illegal drugs' becomes 'es' (E is a term for an ecstasy pill. I am not sure about the 'illegal' bit.).
'run'+'es'='RUNES'
Can you help me to learn more?
(Other definitions for runes that I've seen before include "marks on old tablets" , "Small stones bearing symbols with magic significance" , "Old letters" , "Mysterious letters" , "old characters" .)