Extremely miserable mate goes bust, losing vehicle (9)

I believe the answer is:

paltriest

'extremely miserable' is the definition.

'mate goes bust losing vehicle' is the wordplay.
'mate' becomes 'pal' (I've seen this before).
'goes' becomes 'tries'.
'bust losing vehicle' becomes 't' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pal'+'tries'+'t'='PALTRIEST'

I've seen this clue in The Times.

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