Complex action sealed a reduction in tension (12)

I believe the answer is:

deescalation

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

'tension' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?

'complex action sealed a reduction' is the wordplay.
'complex' is an anagram indicator.
'reduction' means to remove the last letter.
'action'+'sealed'+'a'='actionsealeda'
'actionsealeda' with its last letter removed is 'actionsealed'.
'actionsealed' with letters rearranged gives 'DEESCALATION'.

'in' is the link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.