Welll ... Line-4 is the one that's supposed to rhyme with Line-3, but it's a kind-of awkward rhyme.
"steady" is the word the writer chose to rhyme with "Lady". To me, that's a real stretch.
If I absolutely had to write this limerick for homework, I would probably have written something like
There was a Young Lady whose nose
Was so long that it reached to her toes;
So she hired an Old Lady,
Named Sadie O'Grady,
To help out with that long heavy nose.
Sure it's nonsense. But I fixed the rhyme and the meter.