For non-standard types (inet, cidr, macaddr) you can cast to a known Postgres type with a double colon and the type.
insert into click (ip) values ('127.0.0.1'::inet)
When creating a prepared statement the placeholder marker should be '?::' instead of '?'.
This can be fixed by overriding DBDictionary.getMarkerForInsertUpdate (patch attached) and annotating the field with the non-standard type. Like this:
@Column(columnDefinition = "inet")