Initially find our relaxation in extensive woodland (6)
I believe the answer is:
forest
'extensive woodland' is the definition.
(a forest is a large area of woodland)
'initially find our relaxation' is the wordplay.
'initially' says to take the initial letters.
'relaxation' becomes 'rest' (synonyms).
The first letters of 'find our' is 'fo'.
'fo'+'rest'='FOREST'
'in' is the link.
(Other definitions for forest that I've seen before include "Tree-covered area" , "Best Actor Oscar winner 2006, for 'The Last King of Scotland'" , "eg Sherwood" , "Large area of trees and undergrowth" , "See 15" .)