Friend carried iodine container (4)
I believe the answer is:
pail
'container' is the definition.
(I know that pail is a type of vessel)
'friend carried iodine' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'carried' is an insertion indicator.
'iodine' becomes 'I' (chemical symbol).
'pal' enclosing 'i' is 'PAIL'.
(Other definitions for pail that I've seen before include "A bucket as for water" , "Open-topped container" , "A bucket - the kind Jack and Jill used" , "Cylindrical vessel" , "Vessel for carrying liquids" .)