Sentence:  Hereditary fiefs meant that the king could not refuse to <WSD>enfeoff</WSD> a legitimate, able-bodied heir, but renewal was still required for the successor to exercise any rights or functions associated with the fief. 
Meaning of the word marked with <WSD> tags:  To transfer a fief to, to endow with a fief; to put (a person) in legal possession of a freehold interest.