One with limited freedom to ride the waves, say (4)
I believe the answer is:
serf
'one with limited freedom' is the definition.
'ride the waves say' is the wordplay.
'ride the waves' becomes 'surf' (I've seen this before).
'say' shows a homophone (sound like).
'surf' is a homophone of 'SERF'.
'to' is the link.
(Other definitions for serf that I've seen before include "Bondman" , "Servant, vassal" , "Feudal subject" , "Peasant, agricultural labourer" , "Worker bound" .)