Wiktionary
yield up
vb. 1 To give something against one's will. 2 To disclose something hidden.
WordNet
yield up
v. surrender, as a result of pressure or force
Usage examples of "yield up".
Therewith came Elias and bade the king yield up the castle: For ye may not hold it no while.
Sir Elias, said the king, so will I yield up the castle if I be not soon rescued.
A kings' tear can be cut to yield up to four gems of insight (if the proper enchantments are used).
He'd doubted from the beginning that a live Kharza-kzad would willingly yield up any useful information, but there were ways of compelling a spirit to speak truth.