Has to cut foreign titles in decisive action (6,4)

I believe the answer is:

litmus test

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'has to cut foreign titles in decisive action' is the definition.
I can't tell whether this definition defines the answer.

'has to cut foreign titles in decisive action' is the wordplay.
'has to' becomes 'must' (I've seen this before).
'cut' means to remove the last letter.
'foreign' indicates anagramming the letters (foreign order of the letters).
'in' is an insertion indicator.
'decisive action' becomes 't' (I can't justify this - if you can you should believe this answer much more).
'must' with its last letter taken off is 'mus'.
'titles' anagrammed gives 'littes'.
'mus' going inside 'littes' is 'litmustes'.
'litmustes'+'t'='LITMUS TEST'

Can you help me to learn more?

(Other definitions for litmus test that I've seen before include "Chemical trial" , "Observer may see red after one" .)

I've seen this clue in the Sydney Morning Herald.

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