This is the 12038th most frequent Polish word.
leśną
"Leśną" means "forest" or "woodland" in relation to something (feminine form, e.g., "forest road").
Here, 'leśną' is used as an adjective modifying 'ścieżką', which is the instrumental case of 'ścieżka' (path). It describes the type of path as being associated with the forest.
Podróżuj leśną ścieżką, aby dotrzeć do jeziora.
Travel the forest path to reach the lake.
In this example, 'leśną' describes 'okolicą', which is in the instrumental case of 'okolica' (area). It specifies the characteristic of the area as being forest-like.
Spotkaliśmy grupę ludzi podczas spaceru leśną okolicą.
We encountered a group of people while walking through the forest area.
Here, 'leśną' modifies 'porę', the accusative case of 'pora' (season), highlighting the specific nature of the season as associated with the forest.