Answer: psiloveyou

AnswerCrossword Clue
PSILOVEYOUBeatles hit with the line, "Treasure these few words till we're together"
PSILOVEYOU"Song based on a letter," per McCartney
PSILOVEYOU1964 Beatles tune
PSILOVEYOU1964 Beatles hit
PSILOVEYOUBeatles' billet-doux
PSILOVEYOU'64 Beatles hit