The answer to the crossword question is FEE. The clue ‘Something hidden that’s unpleasant to discover‘ suggests that there is some sort of cost or charge that may not have been expected or previously disclosed. FEE can refer to a variety of different charges, such as a bank fee, service charge, or fine, all of which can be unpleasant to discover. The use of the word ‘hidden‘ implies that this fee may not have been readily apparent, which can add to the unpleasantness of the discovery. Ultimately, the answer to this crossword question is FEE, representing the unpleasant cost or charge that was previously hidden.