The most common and most likely answer to this crossword clue is the 9 letter word PICKETING
I've seen this crossword clue in Financial Times
P
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K
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T
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Buddy explains!
The straight part
We know that "the action of a striker" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the action of a striker = picketing.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PICKETING mean?
PICKETING verb- To protest, organized by a labour union, typically in front of the location of employment.
- To enclose or fortify with pickets or pointed stakes.
- To tether to, or as if to, a picket.
- To guard, as a camp or road, by an outlying picket.
- To torture by forcing to stand with one foot on a pointed stake.
- The act of one who pickets (in any sense).