4 letter word starting with scr spr or str - brother is to mother as fly is to - - - -

Question

Well, scry, stry, and spry are all words, but I guess spry works the best.???

I can't find scry or stry in my dictionary. I don't see the analogy between spry and fly.

oblique is to slanting
timid is to audacious
churlish is to exspensive
willful is to graceful