The most common and most likely answer to this crossword clue is the 8 letter word ISOTHERM
I've seen this crossword clue in The Daily Telegraph
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S
O
T
H
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M
More clues leading to the result ISOTHERM
- Distinctive theory about alternative meteorological line
- Breathes with different rhythm ultimately — indication of temperature
- Contour shows mother is out of shape
- Head of Meteorology differs, first drawing line on her map
- Distinctive theory describes different meteorological feature
- One thus joins the jolly line
- Mother is shifting line on map
- Theory incorporating different line that’s charted to a degree
- Temperature line more confused with this
- Mother is composing a line to the weatherman
Buddy explains!
The straight part
We know that "Weather line on map" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weather line on map = isotherm.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ISOTHERM mean?
ISOTHERM noun- A line on a graph or chart, such as a weather map, along which all the points have the same temperature.