End of a piece of wood shaped to form a mortise joint (5)
I believe the answer is:
tenon
'end of a piece of wood shaped to form a mortise joint' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tenon that I've seen before include "Joint - tonne (anag)" , "Shaped end of piece of wood for slotting into a hole." , "Projection (joins with mortise)" , "Type of hacksaw" , "Piece to fit into mortise" .)