Final answer:
St. Bernard of Clairvaux called for the Second Crusade in the 1140s as a response to the loss of Christian territories in the Holy Land.
Step-by-step explanation:
The cleric who called for the Second Crusade in the 1140s was St. Bernard of Clairvaux. Bernard of Clairvaux was a prominent preacher who inspired believers to join the crusade and wrote the rules for the Knights Templar, one of the new crusading orders. He called for the Second Crusade as a response to the loss of Christian territories in the Holy Land and aimed to mobilize powerful rulers like King Louis VII of France and King Conrad III of Germany.