Six aluminium and sulphur containers (5)
I believe the answer is:
vials
'containers' is the definition.
(vial is a kind of container)
'six aluminium and sulphur' is the wordplay.
'six' becomes 'vi' (roman numeral).
'aluminium' becomes 'al' (Al is the chemical symbol for aluminium).
'and' is a charade indicator (letters next to each other).
'sulphur' becomes 's' ('S' can be a synonym of 'sulphur').
'vi'+'al'+'s'='VIALS'
(Other definitions for vials that I've seen before include "Small glass containers" , "Ampoules" , "Small bottles of medicine" , "Small bottle that contains a drug" , "Vessels" .)