What does the cryptic crossword clue "A bit of heat delineated by weather map (5)" mean?

The definition is "A bit". The wordplay uses a hidden word. Hidden in "a bit of heat delineated by weaTHER Map" The answer is THERM.

A bit of heat delineated by weather map (5)

Independent Cryptic #11785 | 25 Down | 2024-07-18 flower