Thorn from small tree (5)
I believe the answer is:
spine
'thorn' is the definition.
(I know that thorn can be written as spine)
'small tree' is the wordplay.
I cannot quite understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is located in the answer.
'tree' could be 'pine' (pine tree is a kind of tree) and 'pine' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'from' acts as a link.
Can you help me to learn more?
(Other definitions for spine that I've seen before include "Line of vertebrae" , "Strength of character" , "Part of a book" , "Thorn" , "Backbone" .)