General:
* Demanded
* Shouted
* Yelled
* Screamed
* Pleaded
* Begged
* Protested
* Argued
* Complained
* Called out
* Raised their voices
More specific:
* If it's about a crowd: roared, surged, thronged, pressed, swarmed
* If it's about a request: insisted, urged, implored, entreated
* If it's about a protest: demonstrated, rallied, rioted, revolted
* If it's about a sound: thundered, boomed, resounded, echoed
The best synonym will depend on the specific meaning of "clamored" in the sentence.