Well not necessarily. In Spain for instance, a 'release clause' is triggered when a player buys out the remainer of the contract on a pre-agreed amount, this is circumvented by the 'purchasing' club 'loaning' that amount to the player. This specific manner of 'release clause' is very much illegal in the UK so @Happy Blue is correct to a degree.
I think English clubs typically use a 'good faith' clause that promises a player they will enter negotiations when certain conditions are met, not that they will necessarily accept the offer. This is essentially what happened with the Luis Suarez to Arsenal incident, that being 40,000,000 pounds were the bare minimum of entering a negotiation with Liverpool.