Finished work on high trees in swamps (10)

I believe the answer is:

overwhelms

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

'swamps' is the definition.
The definition and answer can be both to do with contact as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?

'finished work on high trees' is the wordplay.
'finished' becomes 'over' ('over' can be similar in meaning to 'finished').
'work' becomes 'w' (physics abbreviation).
'on' is a charade indicator (letters next to each other).
'high trees' becomes 'helms' (I can't justify this - if you can you should give a lot more credence to this answer).
'over'+'w'+'helms'='OVERWHELMS'

'in' is the link.

Can you help me to learn more?

(Another definition for overwhelms that I've seen is " submerges".)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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.