Search: gadfly; cleg
Why: In the In Touch Weekly crossword, #59 across: "Gadfly"
Answer: It's just a fly! Like a horsefly. It has to "bite or annoy livestock." A "cleg" (from Old Norse kleggi) is the same thing. Those are words you can use now. You're welcome!
The word comes from goad. Goadfly. Goad.
Other types of gadfly include the botfly and the warble fly. Don't look them up.
Source: Merriam Webster, The Free Dictionary
The More You Know: When not talking about clegs, botflies, or warble flies, "gadfly" refers to people who upset the status quo by challenging common assumptions or otherwise being annoying. In Plato's Apology, Socrates said he bit Athens out of complacency:
I am a sort of gadfly, given to the state by the God; and the state is like a great and noble steed who is tardy in his motions owing to his very size, and requires to be stirred into life. I am that gadfly which God has given the state and all day long and in all places am always fastening upon you, arousing and persuading and reproaching you.