This is a charade - where different parts of the clue give you separate components that are joined together to form the final answer.
Look for a word meaning 'remain' that comes after something related to a suspicious cook. In Cluedo, one of the suspects is a cook - this gives you the first part. 'On the right side of' tells you where to place the 'remain' word.
Answer: WHITE LIE | WHITE comes from Mrs White (the suspicious cook from Cluedo), and LIE means 'remain'. 'On the right side of' indicates LIE goes after WHITE. A white lie is indeed a porky (rhyming slang: porky pie = lie) that's harmless.