From Longman Dictionary of Contemporary Englishfirst aiderˌfirst ˈaider noun [countable] British English MHsomeone who is trained to give first aid
Examples from the Corpus
first aider• Interview.He sez he went to see if he could help because he's a first aider.• A complete first aid kit has been issued to each first aider which is kept ready to hand at their workplace. 