WordNet sense 1 (restraint that attaches to something or holds something in place):

fastener, fastening, holdfast

WordNet sense 2 (the sterilization of an animal):

altering, neutering

WordNet sense 3 ((histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body):

fixation

WordNet sense 4 (the act of putting something in working order again):

fix, fixture, mend, mending, repair, reparation, repair