I've been practising protecting my hands tonight.
Suppose you have KsKh and the flop is 2s6c9c with 8 bets in the pot. You are first to act.
You should notice that there is a club flush draw on the table. However, if you bet, the next player will be getting 9/1 on a call which is profitable when drawing to a flush. A better play than betting is to check/call until the turn to see if a safe card lands. If it does then bet/raise if doing so will still deny other players the 4/1 required for a profitable call on a flush draw.