Crossword puzzle clue "harder to lift perhaps"

"... ___ again, harder, harder!" (football cheer)

Alt.country singer Case whose "The Worse Things Get, The Harder I Fight, The Harder I Fight, The More I Love You" comes out tomorrow

Harder to lift, perhaps

Harder to plow, perhaps

Harder to climb, perhaps

Harder-won, perhaps

Harder to read, perhaps

Harder to penetrate