Warning by way into woods (6)
I believe the answer is:
forest
'woods' is the definition.
('forest' can be a synonym of 'woods')
'warning by way' is the wordplay.
'warning' becomes 'fore' (I've seen this in other clues).
'by' says to put letters next to each other.
'way' becomes 'st'.
'fore'+'st'='FOREST'
'into' is the link.
(Other definitions for forest that I've seen before include "Large densely wooded area" , "Tree-covered area" , "Large wood" , "Large area of trees and undergrowth" , "Dense woodland" .)