Ebbie, I really have no idea what the answer could be but I think the answer must be a play on words somehow--it's not literally another word that ends in "gry" because, like you said, no others exist. At first I thought it might be "agree" or something like that--with the same sound as "gry" but a different spelling. Maybe check the "gree" suffixes and see if any words fit into the clues. Sorry, that's the best I can do right now, but will think about it...