"More leftfield" implies something that is unconventional, unexpected, or out of the ordinary. Therefore, the antonyms for this phrase would be something that is more well-known, predictable, or mainstream. Some possible antonyms could be "conventional," "traditional," "commonplace," "mainstream," "ordinary," or "typical." These words imply a sense of familiarity and normativity, which is the opposite of "more leftfield." While both have their own unique advantages and disadvantages, it ultimately depends on the context and situation to determine which type of approach is more appropriate.