Fancy a John Lennon song? (7)
I believe the answer is:
imagine
This clue is a double definition.
'fancy' is the first definition.
(I've seen this before)
'a john lennon song?' is the second definition.
(I've seen this in another clue)
(Other definitions for imagine that I've seen before include "John Lennon classic (just think of it!)" , "Form a mental image in the mind" , "Conceive in the mind" , "that Lennon composed" , "A Gemini? (anag)" .)