1. Her nest may become empty if leaves dry. Answer: Mummy. So it's 'if' leaving 'mummify' but what about 'her nest may become empty'
2. Cover around other shoes. Answer: Galoshes.
3. Writer of Campbell's Seabird Cookbook. Answer: Ernest Hemingway.
4. So long wings evident in 6's (see above) work. Answer: A Farewell To Arms
5. Last word in letter from bank. Answer: Sincerely. I get that it's often the last word in a letter but where does 'bank' come in?
6. city embodying mostly flimsy set of morals. Answer: Ethic.
All from a crossword set by Dean Mayers who is in a world of his own and uses very approximate synonyms - grr! Any help appreciated.