Crossword Genius

The meteorologist's line (6)

Ross

I believe the answer is:

isobar

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'the meteorologist's line' is the definition.
(I've seen this in another clue)

'meteorologist's line' is the wordplay.
'meteorologist' becomes 'iso' (I can't explain this - if you can you should believe this answer much more).
'line' becomes 'bar line' (bar line is a kind of line).
'iso'+'bar'='ISOBAR'

Can you help me to learn more?

(Other definitions for isobar that I've seen before include "Line on map connecting places of equal atmospheric pressure" , "Line showing points having equal barometric pressure at a given time" , "Air pressure line on a weather chart" , "It appears on some maps" , "Weather-map line" .)

I've seen this clue in the Evening Standard and The Globe and Mail.
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