1spear·head 
/ˈspiɚˌhɛd/ noun
plural spear·heads /ˈspiɚˌhɛd/ noun [count] : a person, thing, or group that organizes or leads something (such as a movement or attack)
▪ Her book was the spearhead of the clean water movement.
▪ Her book was the spearhead of the clean water movement.
