Guardian Genius 87 - Lavatch

[toalisi]

I have a few of the 'straight' clues solved, but I am struggling to find
the common theme & thereby the substitution code.
Can anyone give me a pointer to get me going?

[kayakamina]

Your best starting point is 26a.

It is a hidden answer which should give a 4 letter for the group you are seeking.

If you then look carefully at the 4 letter word you will see that an alphabetical substitution is suggested. Use the same suggested formula for the other 7 like clues.

The final entries into the grid are nonwords.

[rainblue]

22a also is a fairly good starting point. Mystic Meg ?? try monocled TV presenter.

[toalisi]

Thanks K and rainblue.

I've now got the code and can begin encrypting.

[djmelancourt]

Not an answer, but a question:

Light rain? If so, it makes mum tut.

I believe this to be MIST. Can anyone explain why in that case?

[kayakamina]

If M is T then Mum is TUT

[djmelancourt]

Good grief! Given FISH, how could I miss MIST?

Humble thanks.