Plant's core yielded base for tequila (5)
I believe the answer is:
agave
'base for tequila' is the definition.
(tequila is made from the agave plant)
'plant's core yielded' is the wordplay.
'core' indicates the central letters.
'yielded' becomes 'gave' ('give' can be a synonym of 'yield').
The middle letter of 'plant' is 'a'.
'a'+'gave'='AGAVE'
(Other definitions for agave that I've seen before include "A cactus" , "Succulent plant" , "native growing up in tropical America" , "Tropical plant" , "Spiky succulent" .)