Alternatives to the word fanclub?

What exactly do you want this word to do?

'Fan club' (two words, btw.) is extremely concise.

Lexico's shortest synonyms for Fan and Fanatic:
lover, addict, fanatic, backer, zealot, expert
informal: buff, fiend, freak, bug, nut, maniac, groupie, junkie, jock, crank, geek, buff, -head

Synonyms for Enthusiast add a few more:
admirer, supporter, follower, wizard, pundit, savant
informal: ninja, ham, maven, nerd

There are no snappy synonyms for Member:
subscriber, associate, representative, attender, insider, fellow, comrade, adherent, life member, founder member, card-carrying member
supporter, follower, upholder, advocate, disciple, sectary