The spelling in the manuscript is narwʒ. The shape of the [w] between narwʒ and wei is consistent, as is the [r] between it and streit and the [a] between it and ʒat. The yogh [ʒ] is consistent between it and ʒat as well; it appears Studylight represents the yogh as a [y].
Middle English has no single consistent spelling. Especially for this word, according to the Middle English Dictionary ("narw and narwe") we have:
narw(e adj. Also nareu(e, narewe, narow(e, nareuʒe, narouʒ(e, narouʒh, narough, nareuh, naru(e, narru, narʒ, nargh, narwʒ, narwh, nare & nerue & (early) nearw(e, near(u(we, nerw, nærewe, nærewne, (early SEM) nerewe, (early SWM) nearewe, nearow(e, neruwe, neruh.
While the absence of a vowel between [r], [w], and [ʒ] may send shivers down the spine of a first year Middle English student, we also see this in Middle English with words like borwʒ (modern burrow) and merwʒ (modern marrow).