I could be way off the mark here as things may have changed since I went about seeking garda clearance years ago for a job, but AFAIK you can only obtain/request garda clearance for certain positions within certain organisations where you would be working with vunerable children - the request has to come from an organisation that is recognised such as the HSE or educational boards, or childrens' organisations like Barnardos etc, they don't provide this service to just anyone who requests it.
Obviously references should be checked thoroughly but I think obtaining garda clearance would not be viable.