Field to appeal
Field is saying he will appeal the decision to allow charges to be filed. His chance of success must be close to zero (that comment relates to this stage only, not to eventual guilt) and if he does appeal it will be simply to delay things as long as possible.
A minor inaccuracy in the Herald article. They state he can not stand if he is convicted. Unless he is in jail he can stand, even with a conviction. But if the conviction occurs prior to the election, then he loses his seat immediately and a by-election is called (unless it is within six months of the general election).