The electronic and magnetic properties of the charge neutral iron-sulfur clusters, [4Fe-4S], encapsulated in a semiconducting single-walled carbon nanotube, CNT(17,0), are examined within the density functional theory approach. We verified that for the isolated cluster, due to exchange coupling between the electron spins on iron ions, the antiferromagnetic ground state with the total spin S = 0 is formed. The encapsulation provides the significant charge transfer from the carbon nanotube to the embedded molecule. In consequence, a shift of the molecular levels with broadening of the HOMO-LUMO gap is observed, and the significant p-doping of the surrounding nanotube with narrowing its energy band gap occurs. This transferred charge is found to be localized on the iron centers and contributes to the reduction of the value of the magnetic moments on the iron centers. We find that, the antiferromagnetic arrangement of the magnetic moments on the molecule is preserved after encapsulation and no net magnetic moment is induced on the carbon nanotube. We also ascertained that the considered hybrid system is of the p-degenerated semiconducting type.