Jackson writes "In 1376 a licence to crenellate was reputedly issued to the 'Prior and Convent to enclose and embattle the walls of the Priory'. This wall and a ditch enclosed about ninety acres, and had two gateways." This is not a confusion with the enrolled 1344 licence which Jackson also records. I presume Jackson's source is Ord.
In the 49th Ed. III. the king granted his license to the prior and convent to enclose and embattle the walls of the priory. Part of this wall remained till the last few years at the upper part of the hall-garden, but has fallen beneath the ruthless hand of timeor man ! (Ord)
This is not enrolled in usual rolls (CPR; CChR; CCR). There is a LC to Selby abbey granted in 49 Edw III but it seems unlikely Selby could be misread as Gisburne (the usual medieval version of Gisborough), even in Latin manuscript. Possibly enrolled elsewhere, or roll lost, or erroneous.