Let drop when draught contains iodine, sulphur and chlorine (8)
I believe the answer is:
disclose
'draught contains iodine sulphur and chlorine' is the definition.
I can't judge whether this defines the answer.
'let drop' is the wordplay.
'let' becomes 'disc' (I can't justify this - if you can you should believe this answer much more).
'drop' becomes 'lose' (I've seen this in other clues).
'disc'+'lose'='DISCLOSE'
'when' is the link.
Can you help me to learn more?
(Other definitions for disclose that I've seen before include "Divulge or expose" , "Divulge, reveal" , "Announce" , "Sold ices (anag)" , "Lay bare" .)