Think of a 1970s song (7)
I believe the answer is:
imagine
'think of' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for imagine that I've seen before include "Assume" , "Conjure up in mind, visualise" , "Picture in one's mind" , "Believe to be so, suppose" , "Devise" .)