Join the Freedom Fighters? Don't let that happen! (6)

I believe the answer is:

resist

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'join' is the definition.
The answer and definition can be both to do with social activities as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for resist that I've seen before include "Offer opposition to" , "Stand up to, fight against" , "Refuse to give in to" , "'Withstand, fight against (6)'" , "Withstand, struggle against" .)

I've seen this clue in The Irish Times.

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