Beware opening in rock, should one? (5)

I believe the answer is:

caver

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'should one?' is the definition.
I can't tell whether this defines the answer.

'beware opening in rock' is the wordplay.
'beware' becomes 'cave' (old-fashioned term meaning 'look out').
'opening in' says to take the initial letters.
The initial letter of 'rock' is 'r'.
'cave'+'r'='CAVER'

Can you help me to learn more?

(Other definitions for caver that I've seen before include "Potholer" , "Speleologist" , "Underground explorer" .)

I've seen this clue in The Times.

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