Wright's message is made clear in the first, second and last stanzas: it is foreshadowed in the first and second and illustrated in the last; the third stanza undergirds the coming message with experiential knowledge, the knowledge that women have that girls don't have:
reduces to a neat
compression fitting in the smallest space (stanza 1)
that glimpse of unobstructed waiting green.
Run, run before you're seen. (stanza 2)
Stanza 1 prepares for something of value that will compressed to fit in a small space: "compression fitting in the smallest space." Stanza 2 prepares us for obstructions that exist blocking that seemingly "unobstructed waiting green." Stanza 3 points out the difference between what women know and what little girls know.
women know the scale of possibility,
the limit of opportunity, (stanza 3)
Stanza 4 explains that once little girls become women, the "ancient dance" is one that traps dreams, closes them in, folds them up and closes them away in a cupboard:
And they can demonstrate it in a dance.
First pull those wallowing white dreams down,
spread arms: then close them. Fold
those beckoning roads to some impossible world,
put them away and close the cupboard door.
Thus the message is that while young girls may dream of roads ahead and "waiting green" opportunity that is not obstructed by anything other than comforting white wash gamboling on the happy wind, women have seen the fence, have seen the obstructions to the "impossible roads," have seen that dreams, hope and opportunity are closed in a cupboard.