Heading for Exmoor, oxygen-fuelled females take a hike (3,3)

I believe the answer is:

eff off

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'heading for exmoor oxygen-fuelled females take a hike' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'heading for exmoor oxygen-fuelled females take a hike' is the wordplay.
'heading for' says to take the initial letters.
'take' means one lot of letters goes inside another.
'a hike' becomes 'ff' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The first letters of 'exmoor oxygen fuelled females' is 'eoff'.
'eoff' going around 'ff' is 'EFF OFF'.

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I've seen this clue in The Guardian.

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