Copying Content Taxonomy Field values from referenced node

I've failed to get my head around this and hope someone can give me some pointers!

I want to copy content taxonomy field values from a referenced node of the same type.

This is my best (confused!) attempt so far:

1. Load a referenced node.

This works fine - I can copy text (and other) field values OK.

2. Load a vocabulary.

I'm not confident that I need to do this but I'm loading the vocabulary used for the content taxonomy field.

3. Load a term.

This is something I'm trying in desperation without any understanding. I'm doing "Select by term id", using the token [referenced_node:field_taxonomy-tid] where field_taxonomy is the content taxonomy field in question.

4. Populate a field.

At this point I don't have a clue. I've tried a few things with php snippets such as,

return array(
0 => array('tid' => [referenced_node:field_taxonomy-tid]),
);

Also the same with [referenced_node:field_taxonomy-term-raw], and using 'value' and 'term' instead of 'tid', but without any success.

Can anyone help or point me to somewhere that might help?

An additional problem is that once I've got this sorted for a single-term taxonomy I need to handle a multiple-term one!