Are caught trespassing in the land (4)
I believe the answer is:
acre
'land' is the definition.
(I've seen this before)
'are caught trespassing' is the wordplay.
'caught' means one lot of letters goes inside another.
'trespassing' becomes 'c' (I am not sure about this - if you are sure you should believe this answer much more).
'are' enclosing 'c' is 'ACRE'.
'in the' is the link.
Can you help me to learn more?
(Other definitions for acre that I've seen before include "Muslims here besieged" , "Unit of area of 4,840 square yards" , "Care about the land measure" , "Race (anag.)" , "Unit of land measurement" .)