The same letter can be added to each of the words or names below to create a list of new words, which, when anagrammed, will have something in common.

KEW
MUG
AMOS
TREES
CRISCO
DANGER
STAMINA
REPOSING

HINTS:
#1: The added letter is A.
#2: The new words are all names of places.

Answer:

Inserting the letter A into each word or name and re-arranging the letters gives the name of an ISLAND:

WAKE
GUAM
SAMOA
EASTER
CORSICA
GRENADA
TASMANIA
SINGAPORE

Credit: Will Shortz
NPR Weekend Edition Sunday Puzzle
Sept. 6, 2009 - "A" TEST OF ISLANDS