Joint initially twisted in boggy ground (5)
I believe the answer is:
mitre
'joint' is the definition.
(I know that mitre is a type of joint)
'initially twisted in boggy ground' is the wordplay.
'initially' says to take the initial letters.
'in' is an insertion indicator.
'boggy ground' becomes 'mire' (I've seen this in another clue).
The first letter of 'twisted' is 't'.
't' put within 'mire' is 'MITRE'.
(Other definitions for mitre that I've seen before include "Bishop's headgear - joint" , "symbol of ecclesiastical authority" , "See boss gear up" , "Bishop's cap - wood joint" , "Bevelled joint that forms a corner" .)