First character donated plant (5)
I believe the answer is:
agave
'plant' is the definition.
The answer is an example.
'first character donated' is the wordplay.
'first' says to put letters next to each other.
'character' becomes 'a'.
'donated' becomes 'gave' (give can mean to donate).
'a' next to 'gave' is 'AGAVE'.
(Other definitions for agave that I've seen before include "Succulent plant" , "Tropical plant" , "source of tequila" , "Spiky succulent" , "native growing up in tropical America" .)