In place of the mixed sets of woods (7)
I believe the answer is:
forests
'woods' is the definition.
('forest' can be a synonym of 'wood')
'in place of the mixed sets' is the wordplay.
'in place of' becomes 'for'.
'the mixed' is an anagram indicator.
'sets' anagrammed gives 'ests'.
'for'+'ests'='FORESTS'
'of' acts as a link.
(Other definitions for forests that I've seen before include "Large woods" , "Large, densely-wooded area" , "Densely wooded areas" , "Woodlands" .)