Plenty of room for a 'Trek' (5)

I believe the answer is:

space

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'plenty of room' is the definition.
'space' can be an answer for 'room' (I've seen this in another clue). I am not certain of the 'plenty of' bit.

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for space that I've seen before include "Empty area, may be outer" , "sci-fi theme" , "Interstellar region" , "Cosmos" , ""The final frontier"" .)

I've seen this clue in the Evening Standard.

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