People leaving money behind in trucks? (7)

I believe the answer is:

tippers

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'people' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'money behind in trucks?' is the wordplay.
'money' becomes 'tip' (money given for service).
'behind in trucks?' becomes 'pers' (I can't explain this - if you can you should believe this answer much more).
'tip'+'pers'='TIPPERS'

'leaving' is the link.

Can you help me to learn more?

I've seen this clue in The Times.

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