Joint fishing expedition's focus (5)

I believe the answer is:

hinge

I'm a little stuck... Click here to teach me more about this clue!

'joint' is the definition.
(hinge joint is a kind of joint)

'fishing expedition's focus' is the wordplay.
'HINGE' is hidden within the letters.
However, I'm uncertain how this is indicated.

Can you help me to learn more?

(Other definitions for hinge that I've seen before include "Door pivot" , "Pivotal point" , "Fastening for door etc" , "door open because of this?" , "Joint on which something turns" .)

I've seen this clue in the Sydney Morning Herald.

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