Piece of land used in nuclear experiments (3)
I believe the answer is:
are
'piece of land' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'in nuclear experiments' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ARE' is hidden within 'nuclear experiments'.
'used' acts as a link.
Can you help me to learn more?
(Other definitions for are that I've seen before include "(We/you/they) exist" , "(They/you/we) exist" , "Unit of land measure equal to 100 square metres" , "is for more than one" , "Exist; square measure" .)