Yes, but not easily. Wagering comes in two phases, free spins and a cash bonus. A good number of betting sites offering wager free spins require the gamer to play with the spins, where the winnings are not subjected to a wager. From here the gamer can withdraw.
However, all cash bonuses have to undergo between X30 and X50 for them to mature for withdrawal. This means that online casino bonuses must be played through a lot before the funds can be withdrawn or converted into regular deposits. On top of that, different games contribute towards the requirements differently, so while betting on a slot game can make the process faster, betting on live roulette will take considerably longer.