Crossword Genius

Line on taxi mostly grease (4)

Ross

I believe the answer is:

lube

'grease' is the definition.

'line on taxi mostly' is the wordplay.
'line' becomes 'l'.
'on' is a charade indicator (letters next to each other).
'taxi' becomes 'uber'.
'mostly' means to remove the last letter.
'uber' with its last letter taken away is 'ube'.
'l'+'ube'='LUBE'

(Other definitions for lube that I've seen before include "oil" , "Grease (abbr)" .)

I've seen this clue in The Guardian.
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