Slave man, one found in auction (5)
'slave' is the definition.
(slave in ancient Sparta)
'man one found in auction' is the wordplay.
'man' becomes 'he'.
'one found in auction' becomes 'lot' (I can't justify this - if you can you should give a lot more credence to this answer).
Can you help me to learn more?
(Other definitions for helot that I've seen before include "He's bound to land", "Hotel (anag) - serf", "Greek serf", "Spartan serf", "Serf of ancient Sparta".)