Today’s crossword is based on words that can be combined with the word ‘DOWN’ to form new words.
In all clues, the first part and the letter-count leads you to the word and the second part defines the meaning of the new word formed when you combine it with DOWN.
e.g. a natural phenomenon measured in knots; standing in the direction of airflow. (4)
This would be WIND (first half) and the second half defines DOWNWIND.
Hint: Start with clue 4-down to quickly understand the format