Densely wooded area (6)
I believe the answer is:
forest
'densely wooded area' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for forest that I've seen before include "Large, densely-wooded area" , "eg Sherwood" , "Large area of woodland" , "Thief (rhyming slang)" , "Large densely wooded area" .)