Reportedly waves to slave? (4)
I believe the answer is:
serf
'to slave?' is the definition.
(I've seen this before)
'reportedly waves' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'waves' becomes 'surf' (surf can mean foam from waves).
'surf' sounds like 'SERF'.
(Other definitions for serf that I've seen before include "Person required to work for a lord" , "Servant, vassal" , "One bound to the land" , "Peasant, agricultural labourer" , "Feudal estate worker" .)