Leaders yield - union chiefs can access plant (5)
I believe the answer is:
yucca
'plant' is the definition.
'leaders yield union chiefs can access' is the wordplay.
'leaders' says to take the initial letters.
The first letters of 'yield union chiefs can access' is 'YUCCA'.
(Other definitions for yucca that I've seen before include "Tropical American liliaceous plant" , "Tall, strong, evergreen plant" , "Plant of the Agavaceae family" , "Ornamental plant" , "Garden plant from Mexico" .)