Crossword Genius

Girl anything but restrained climbing tree (7)

Ross

I believe the answer is:

annatto

I'm a little stuck... Click here to teach me more about this clue!

'tree' is the definition.
(I've seen this before)

'girl anything but restrained climbing' is the wordplay.
I cannot really see how this works, but
'girl' could be 'anna' and 'anna' is found in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for annatto that I've seen before include "Orange colouring" , "Colouring matter" , "food colouring" , "dyestuff" , "Food colourant" .)

I've seen this clue in The Times.
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