Possible Clues:

• Saint ____ was the “Apostle to the Picts”
• Saint who converted Scotland to Christianity
• Iona's saint
• Irish missionary saint
• Missionary, in middle of crossword, having soft drink brought round
• Saint who established the monastery on Iona
• Missionary's short newspaper piece, book, and article
• Iona missionary
• Iona monastery saint
• Finder (and loser) of America? A saint!