Joined middle of the road junction (7)
I believe the answer is:
adjunct
'joined middle' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'of the road junction' is the wordplay.
'of' says the answer is hidden in the clue.
'ADJUNCT' is hidden within 'the road junction'.
Can you help me to learn more?
(Other definitions for adjunct that I've seen before include "Something added, but not essential" , "Supplement" , "'Assistant, professor say (7)'" , "Incidental extra" , "Supplementary part" .)