Political party member opens weird joint (4)

I believe the answer is:

whip

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'political party member' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'opens weird joint' is the wordplay.
'opens' says to take the initial letters (use the opening letters).
'joint' becomes 'hip' (part of body).
The first letter of 'weird' is 'w'.
'w'+'hip'='WHIP'

Can you help me to learn more?

(Other definitions for whip that I've seen before include "Political officer who ensures party members attend and vote" , "Party disciplinarian" , "Politician who enforces discipline in the party" , "defeat" , "He maintains discipline among members" .)

I've seen this clue in The Irish Times.

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