I was in a similar situation recently. I was advised to have the document sent to be apostilled in India. I sent it to some relatives in India who organised this and had it returned to me. I'm not sure that you can get a Police Clearance Certificate issued by an Indian authority apostilled in the UK.

Hi there,
Have you had any luck sorting this out with the Irish authorities? I ask because I'm facing exactly the same problem, though this time, with the Italian authorities. Any advice would be much appreciated.