Plant used to make mescal (5)
I believe the answer is:
agave
'plant used to make mescal' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for agave that I've seen before include "Tropical plant" , "Succulent plant" , "Plant, source of sisal" , "source of tequila" , "A cactus" .)