Shoot fluorine and iodine over 50 metres (4)
I believe the answer is:
film
'shoot' is the definition.
(I know that shoot can be written as film)
'fluorine and iodine over 50 metres' is the wordplay.
'fluorine' becomes 'F' (F is the chemical symbol for fluorine).
'and' says to put letters next to each other.
'iodine' becomes 'I' (chemical symbol).
'over 50' becomes 'l' (Roman numeral. I am not sure about the 'over' bit.).
'metres' becomes 'm'.
'f'+'i'+'l'+'m'='FILM'
Can you help me to learn more?
(Other definitions for film that I've seen before include "Moving picture" , "Cinema celebrity" , "Motion picture" , "Shoot - thin layer" , "Flick" .)