Plant adult passed on (5)
I believe the answer is:
agave
'plant' is the definition.
The answer is an example.
'adult passed on' is the wordplay.
'adult' becomes 'a' (abbreviation).
'passed on' becomes 'gave' ('give' can be a synonym of 'pass on').
'a'+'gave'='AGAVE'
(Other definitions for agave that I've seen before include "A cactus" , "plant in Mexico" , "Plant, source of sisal" , "Spiky succulent" , "source of tequila" .)