Tropical plant Auntie originally donated (5)
I believe the answer is:
agave
'tropical plant' is the definition.
(I've seen this before)
'auntie originally donated' is the wordplay.
'originally' says to take the initial letters.
'donated' becomes 'gave' (I've seen this before).
The initial letter of 'auntie' is 'a'.
'a'+'gave'='AGAVE'
(Other definitions for agave that I've seen before include "Succulent; daughter of Cadmus" , "Spiky succulent" , "Succulent plant" , "native growing up in tropical America" , "source of tequila" .)