Band whose song "Train of Thought" starts with the lyric "He likes to have the morning paper crossword solved" (3)
I believe the answer is:
aha
(Other definitions for aha that I've seen before include "Expression of surprise, satisfaction or triumph" , "Palindromic exclamation of triumph or surprise" , "Exclamation of triumph or surprise, a palindrome" , "I see!" , "Exclamation of triumph or mockery, a palindrome" .)