What does the cryptic crossword clue "Section in a board mobilising for environmentalists' goal (15)" mean?

The wordplay uses an anagram. anagram of SECTION + IN + A + BOARD = DECARBONISATION The answer is DECARBONISATION.

Section in a board mobilising for environmentalists' goal (15)

Daily Mail Cryptic #17140 | 6 Down | 2023-07-13 flower