Tension on kilometre journey (4)

I believe the answer is:

trek

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'journey' is the definition.
(I know that trek is a type of journey)

'tension on kilometre' is the wordplay.
'tension' becomes 't' (abbreviation for surface tension).
'on' becomes 're' (regarding).
'kilometre' becomes 'k' (this might be a standard abbreviation I've not previously seen).
't'+'re'+'k'='TREK'

Can you help me to learn more?

(Other definitions for trek that I've seen before include "Long and difficult journey" , "A long hard march" , "Great journey" , "Long and difficult trip" , "Extended journey" .)

I've seen this clue in The Irish Times.

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