A joint the Spanish bend (5)
I believe the answer is:
elbow
'a joint' is the definition.
(elbow is a kind of joint)
'the spanish bend' is the wordplay.
'the spanish' becomes 'el'.
'bend' becomes 'bow' (bowing is a kind of bending).
'el'+'bow'='ELBOW'
(Other definitions for elbow that I've seen before include "part of the body" , "Major arm joint" , "Nudging joint?" , "Hinge joint" , "Hinged joint" .)