临场 ('upon arriving at the scene') +
发挥 ('to bring out / give play to one's ability') = how you actually do once you're in the room — exam, interview, sports match, performance. Usually paired with quality words:
临场发挥得好/
不好 ('performed well/badly on the day'),
临场发挥失常 ('choked / off form'),
临场发挥超常 ('exceeded expectations on the day').