What is the word?

It looks like hegh-stald meaning virgin. It’s also spelled hægsteald, with the etymology reported by Revealing Words as:

the sense slips from Germanic roots of hag as enclosure or fence + steald as settlement or dwelling, to suppositions about a dependant young warrior or household retainer, hence unmarried and without his own household, to novice (tiro) and on to the religiously inflected celibate, and virginity.

See also

• A Compendious Anglo-Saxon and English Dictionary
• A Dictionary of the Anglo-Saxon Language