The point of a crooked thorn (5)
I believe the answer is:
north
'the point' is the definition.
(north is a kind of point)
'a crooked thorn' is the wordplay.
'a crooked' is an anagram indicator.
'thorn' is an anagram of 'NORTH'.
'of' is the link.
(Other definitions for north that I've seen before include "Compass bearing" , "To the left of one who is facing east" , "PM 1770-82" , "Boreal; South's opposite" , "Top of most maps" .)