The most common and most likely answer to this crossword clue is the 8 letter word DOWNWASH
I've seen this crossword clue in The Guardian
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Buddy explains!
The straight part
We know that "Current that’s forced lower" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case current that’s forced lower = downwash.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 DOWNWASH mean?
DOWNWASH noun- Downward air turbulence caused by a propeller or jet, but especially by helicopter blades
- The downward motion of air as a result of eddies behind a wing or chimney, etc.