Type of joint (5)
I believe the answer is:
mitre
'type of joint' is the definition.
(I know that mitre is a type of joint)
This is the entire clue.
(Other definitions for mitre that I've seen before include "Bishop's cap - wood joint" , "Bishop's headwear" , "that goes over a cleric's head?" , "top?" , "See boss gear up" .)