Possible Clues:

• John Lennon classic (just think of it!)
• Fancy Head of Intelligence cracked Enigma
• John Lennon's biggest solo hit
• Fancy a chart-topping single
• Form an image in the mind
• Feel slim? A GI needs sandwiches
• Pretend ... and #3 on the list
• Fancy picture frames in
• Can you picture, that is to say, about Mother and what'll ruin her?
• Wise men entering in appropriate direction in picture