Second gardener donated succulent plant (5)
I believe the answer is:
agave
'succulent plant' is the definition.
(I've seen this before)
'second gardener donated' is the wordplay.
'second gardener' becomes 'a' (2nd letter of 'gardener').
'donated' becomes 'gave' (give can mean to donate).
'a'+'gave'='AGAVE'
(Other definitions for agave that I've seen before include "A cactus" , "Spiky succulent" , "Tropical plant" , "native growing up in tropical America" , "Plant, source of sisal" .)