Science.

[breffni]

Reasons; what, in science, bring about effects. ?A????
The three shy characters drink this! ??A???

[factor-fiction]

causes

[boxtops]

causes

[HowardKennitby]

shandy

[factor-fiction]

I can see the SHY but I can't see where the AND comes from and where the THREE fits in

[HowardKennitby]

S, H and Y

[squarebear]

Three characters, S, H and Y.
A character is another name for a letter.

[factor-fiction]

Thanks. I wouldn't have got that- mind you, from the title I was looking for a Science related solution

[breffni]

Many thanks to all who replied so promptly, almost completed just another two: Recognise that the head of a dahlia is what's worth planting s?e?.
Planned to have removed the autograph,?e?i?n?d.

[HowardKennitby]

designed

[grasscarp]

seed and resigned is my guess

[grasscarp]

designed is better

[breffni]

Many thanks to all and A Happy New Year.