Small piece of land seized by crazy fool (7)
I believe the answer is:
mislead
'fool' is the definition.
(I know that fool can be written as mislead)
'small piece of land seized by crazy' is the wordplay.
'small piece of land' becomes 'isle' (I've seen this before).
'seized by' means one lot of letters goes inside another.
'crazy' becomes 'mad' (synonyms).
'isle' put into 'mad' is 'MISLEAD'.
(Other definitions for mislead that I've seen before include "Fool" , "Take someone in the wrong direction" , "Cause someone to believe something is not true" , "Cause someone to have a false belief" , "Deceive" .)