Striking hard criminal using harsh language (10)

I believe the answer is:

concussing

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

'striking hard' is the definition.
Although both the answer and definition are present participle verbs, I cannot see how one could define the other.

'criminal using harsh language' is the wordplay.
I cannot quite understand how this works, but
'criminal' could be 'con' (abbreviation for 'convict') and 'con' is found in the answer.
'language' could be 'c' (C is an example) and 'c' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The 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.