Cryptic

[hardyboy]

Forecast cover for military advance (7,4). Thank you for ideas and Happy New Year to all

[charity-baker47]

any letters hardyboy

[hardyboy]

No letters just two words 7 and 4 letters. Birnam wood fits the clue perfectly but is only 6 and 4.

[fiction-factory]

Birnham Wood?
I don't see the parsing though

[fiction-factory]

Can we help with one crossing clue just to give us/confirm one letteer?

[hardyboy]

Oh maybe it is Birnham wood. My Macbeth has it spelt Birnam.

[fiction-factory]

Is the clue definitely forecast or forest?

[hardyboy]

This is just a quiz with clues not a crossword so there are no helpful letters.

[fiction-factory]

Both spelling seem to appear in different versions.
I don't understand the wordplay though

[hardyboy]

Definitely Forecast

[fiction-factory]

Is there a theme to the quiz then please?

[fiction-factory]

Okay, you seem happy with it but I don't see how the clue by itself leads to that answer

[hardyboy]

I think the trees were helpful . Maybe I am getting it totally wrong

[hardyboy]

The theme is anything to do with trees- sorry I should have mentioned that before

[dannyk13]

Possibly Fore(ca)st

[fiction-factory]

Thanks.
I'm not sure why the clue says forecast though

[fiction-factory]

Thanks danny. Yes, I'd thought of that for the forest but thought it seemed a bit contrived, but depending on the style of other clues it could be that

[fiction-factory]

Birnam does seem to be the more common spelling

[Tilly2]

The witches foretold that Birnham Wood would move towards Dunsinane Castle.

I think it's a clever clue.

[fiction-factory]

Thanks Tilly. You know your Shakespeare far better than I do. Are you happy with the spelling (Birnham rather than Birnam)?

[hardyboy]

Thank you Tilly for explaining. It has been a very clever cryptic quiz, in fact far too clever for me.