Ethel is correct in asking him to 'gut and clean' - though it is very easy to do yourself.
Put a bit of newspaper on you work surface and get a sharp knife. Slit the fish open along the belly from the anal fin (the one nearest the tail), up to the head (once described to me as just before where the "chin" should be!). This will expose the 'body cavity'.
Pull out the stomach and bits by running your finger through the cavity - trim any remaining bits with the knife.
Rinse the cavity under the tap and pat dry with kitchen paper.
Wrap up the newspaper and bin.
Done !!