Film to make your head swim (7)
I believe the answer is:
vertigo
'film' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for vertigo that I've seen before include "Lightheadedness, dizziness" , "unbalanced feeling" , "Feeling of dizziness generated by heights" , "Sensation brought on by great heights" , "Forty Thieves' password" .)