Chemical can turn up with a ceremonial (7)
I believe the answer is:
nitrite
'chemical' is the definition.
(I've seen this before)
'can turn up with a ceremonial' is the wordplay.
'can' becomes 'tin' (both are metal containers).
'turn up' says the letters should be written backwards.
'with' says to put letters next to each other.
'a ceremonial' becomes 'rite' (I've seen this in another clue).
'tin' in reverse letter order is 'nit'.
'nit'+'rite'='NITRITE'
(Other definitions for nitrite that I've seen before include "Chemical" , "Radical" , "salt" , "compound" .)