An enhanced CRB check can show any information which is deemed relevant by a senior police officer. If your new check is for the same type of work as the original one was for it's extremely unlikely that the allegation which led to your arrest will show up.
However, for example, someone who was arrested after an allegation of a sexual offence against a child might find that the information isn't shown if they apply to work with vulnerable adults but is shown if they seek to work with children.
Chris