Unscrupulous filming of marksmanship? (13)

I believe the answer is:

sharpshooting

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'unscrupulous filming of marksmanship?' is the definition.
I can't judge whether this definition defines the answer.

'unscrupulous filming' is the wordplay.
'unscrupulous' becomes 'sharp' (I can't explain this - if you can you should believe this answer much more).
'filming' becomes 'shooting' ('shoot' can be a synonym of 'film').
'sharp'+'shooting'='SHARPSHOOTING'

Can you help me to learn more?

(Another definition for sharpshooting that I've seen is " Expert firing".)

I've seen this clue in The Irish News.

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