Wading bird that may be found in wood (4)
I believe the answer is:
knot
This clue is a double definition.
'wading bird' is the first definition.
(knot is a kind of wading bird)
'wood' is the second definition.
(I know that knot is a type of wood)
'that may be found in' is the link.
(Other definitions for knot that I've seen before include "complex problem" , "Tie; sandpiper" , "Tied fastening" , "Hard irregularity in timber - interlacing of cord" , "Hard mass in tree trunk at branch joint" .)