POLICE in Inverness are to clamp down on anti-social behaviour, including youngsters who hang round street corners making a nuisance. Persistent members of large, noisy teenage groups causing problems will be taken back to their parents by officers who will explain the situation even if the youngsters have not committed a crime. Concerns had been raised at a packed public meeting in Lochardil, Inverness, that teenagers were in some cases was sending out ''intimidatory'' messages to older people. Drummond Councillor Margaret MacLennan said: ''The thing is that is they do become very intimidating once they get into larger groups.''