This is a container clue - one element is placed inside another element to form the answer.
Look for a medical abbreviation for a risk of unprotected sex, then put it inside the abbreviation for Edinburgh's national library (with 'one' represented as a number).
Answer: INSTILS | STI (sexually-transmitted infection) goes inside I (one) + NLS (National Library of Scotland) to give I-STI-NLS = INSTILS