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HiddenServicePort VIRTPORT [TARGET]
Configure a virtual port VIRTPORT for a hidden service. You may use this option multiple times; each time applies to the service using the most recent HiddenServiceDir. By default, this option maps the virtual port to the same port on 127.0.0.1 over TCP. You may override the target port, address, or both by specifying a target of addr, port, addr:port, or unix:path. (You can specify an IPv6 target as [addr]:port.) You may also have multiple lines with the same VIRTPORT: when a user connects to that VIRTPORT, one of the TARGETs from those lines will be chosen at random.
HiddenServicePort 1234 188.8.131.52:1234
In your updated case (which seems to be the inverse of "I want to forward [...] to the clearnet"), you want some non-onion site to display the content of an onion. This will require at least some form of proxy to fetch content from the tor network. What you seem to be describing is Tor2Web.