Finished work on high trees in swamps (10)

I believe the answer is:

overwhelms

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'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 (Crosaire) and the Irish Times.

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