Crossword Genius

Front line? (6)

Ross

I believe the answer is:

isobar

'front line?' is the definition.
(I've seen this in another clue)

This is the entire clue.

(Other definitions for isobar that I've seen before include "Weather-map line" , "One showing pressure" , "Line on map connecting places of equal atmospheric pressure" , "Line joining places of equal barometric pressure" , "feature on some maps?" .)

I've seen this clue in The Sun and the Financial Times.
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