Spiky plant found in country estates (3)
I believe the answer is:
rye
'spiky plant' is the definition.
(type of cereal plant with spiky growths)
'in country estates' is the wordplay.
'in' indicates the answer is hidden within the clue.
'RYE' is hidden within 'country estates'.
'found' is the link.
(Other definitions for rye that I've seen before include "Grass - whiskey" , "One of Cinque Ports" , "Grass related to wheat" , "Cereal used for making whiskey" , "(Gypsy) gent; type of bread, whiskey" .)