Changing Ends 4

Sometimes, compilers like to make life difficult for you: they create clues which are much like those in Changing Ends 3, but instead of giving you the word that you have to alter, they just give you a definition of it. So, for example, “Not fast to change ends of nail in wintry weather (4)”: Not fast = SLOW Substitute the first letter of NAIL (N) for the last letter of NAIL (L) in SLOW, and you get SNOW = wintry weather. Similarly, “Junk e-mails change ends of mailboxes in towns with natural springs (4)”: junk e-mails = SPAM, but if you substitute the last letter of MAILBOXES (S) for the first letter of MAILBOXES (M) in SPAM, you get SPAS= towns with natural springs. If you enjoy my crosswords, please do check out the Cryptic Mystic's YouTube channel - a brilliant resource for beginner and developing cryptic crossworders, which has been kind enough to feature one of my puzzles: https://www.youtube.com/@The_Cryptic_Mystic