Move north - that's sharp (5)
I believe the answer is:
thorn
'that's sharp' is the definition.
(sharp part of a plant)
'move north' is the wordplay.
'move' indicates an anagram (I've seen 'moving' mean this).
'north' with letters rearranged gives 'THORN'.
(Other definitions for thorn that I've seen before include "problematic point" , "A vegetable spike" , "Sharp-pointed stem-tip" , "Spike on a rose bush" , "Sharp-pointed tip on a stem" .)