guardian genius 75

[mischka]

1 down ''In river, left behind Indian sailor that can be commanded'' (8) I think river is Dee, giving
DE****ABLE, but nothing seems to really fit

15 down, ''Girl, what's more, turned up to conceal chemical compound'' (10)... D*S*L***D*

20 down, ''Communications system isn't late for servicing'' (8), I*T***A*

[wallacia]

15d,disulphide.