Hard lump in wood (4)
I believe the answer is:
knot
(Other definitions for knot that I've seen before include "Difficult problem" , "To secure < > bird" , "Fastening formed by tying string etc" , "Entwine" , "Tie, hitch" .)
I believe the answer is:
knot
(Other definitions for knot that I've seen before include "Difficult problem" , "To secure < > bird" , "Fastening formed by tying string etc" , "Entwine" , "Tie, hitch" .)