Sentence:  [...] if these Vpstarts and <WSD>mushrump</WSD> nobles, were but permitted to bee about the Kings Person in his youth, they would afterwards by that meanes so purchase his favour, that they would become so powerfull, when hee should attaine to maturitie of yeares, that all the Honours, Possessions, and lines of the ancient Nobilitie of this Realme would bee in danger, to bee subject to their wills [...] 
Meaning of the word marked with <WSD> tags:  Upstart, a person who has quickly and undeservedly gained their position, power or wealth.