Well built redhead interrupting research (6)

I believe the answer is:

sturdy

I'm a little stuck... Click here to teach me more about this clue!

But I can't explain it at all! Could you help me understand?

(Other definitions for sturdy that I've seen before include "Stalwart, stout, tough" , "Strongly and solidly built" , "Strong and solidly built" , "Strong, solid" , "Well-built - strapping" .)

Want a hint initially instead of a full solution? Install my app