Mine working for Spike useful in upward mobility? (5)

I believe the answer is:

piton

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'spike useful in upward mobility?' is the definition.
'piton' can be an answer for 'spike' (I've seen this before). I'm not sure about the 'useful in upward mobility?' bit.

'mine working' is the wordplay.
'mine' becomes 'pit' (as in a mining pit).
'working' becomes 'on' (e.g. a machine is working or on).
'pit'+'on'='PITON'

'for' acts as a link.

Can you help me to learn more?

(Other definitions for piton that I've seen before include "Spike to support a climber" , "Spiked climbing aid" , "Peg driven into rock as climbing support" , "What mountaineer requires" , "Mountaineer's metal spike" .)

I've seen this clue in The Times.

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