Entrapment is a legal defense, but it is unique in that it is an affirmative defense. Also, what one jury will consider entrapment, another may not.
It's also important to remember that the entrapment defense requires the defendant to admit to committing the crime, and then PROVE that the only reason he committed the crime was that the government gave him unreasonable incentive to commit the crime. The key is unreasonable. The government is allowed to provide a reasonable incentive, and create an opportunity for someone to commit a crime. However, they cannot provide an incentives that would convince an otherwise law abiding citizen to break the law.
AskJeeves turns up a decent brief explanation: "In jurisprudence, entrapment is a procedural defense by which a defendant may argue that they should not be held criminally liable for actions which broke the law, because they were induced (or entrapped) by the police to commit said acts. For the defense to be successful, the defendant must demonstrate that the police induced an otherwise unwilling person to commit a crime. However, when a person is predisposed to commit a crime, offering opportunities to commit the crime is not entrapment."
It's a gamble for a defendant, because it requires they confess, and then shifts the burden of proof to the defense to show that the government acted improperly.
A practical example is a drug deal in which a person offers to buy drugs at a price much higher than what would normally be expected. For example a UC offers to buy 100 pills of X at $20 per pill, and the local price is $15-$25. If the suspect refuses the deal, but the UC counters with $50 per pill, and the suspect affects, that case MAY be a good candidate for an entrapment defense, because it was such an unreasonable price that an otherwise innocent person may take that one deal to make quick cash. However, to attempt that defense the person will need to confess, and then prove that the government was unreasonable in their incentive. Big gamble for a defendant.
However, real cases are not that clear cut because LE agents are not looking to create criminals, they are looking to catch real criminals. In addition most half way intelligent ( and most are only half way) won't accept outrageous deals because they will get suspicious.
So no entrapment is not acceptable, and LE agencies do not attempt to entrap suspects because that creates a defense.