The most common and most likely answer to this crossword clue is the 9 letter word ABATEMENT
I've seen this crossword clue in The Times
A
B
A
T
E
M
E
N
T
More clues leading to the result ABATEMENT
- Subsidence worried crew in Lambeth periodically
- A criminal securing crooked mate’s remission
- Sailor resorted to cannibalism. It finally provides relief
- Sailor messed with crew before temperature drop
- Heartless batsmen eat out causing interruption of action
- Subsidence in a cellar? Time for spades
- Sailor and soldiers consumedbefore initial temperature reduction
- Decline a bet meant to be lost
- Badly beaten, team, without energy, is weakening
Buddy explains!

The straight part
We know that "Subsidence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case subsidence = abatement.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 ABATEMENT mean?
ABATEMENT noun- The act of abating, or the state of being abated; a lessening, diminution, or reduction; a moderation; removal or putting an end to; the suppression of.
- The amount abated; that which is taken away by way of reduction; deduction; decrease; a rebate or discount allowed; in particular from a tax.
- A mark of dishonor on an escutcheon; any figure added to the coat of arms tending to lower the dignity or station of the bearer.
- The action of a person that abates, or without proper authority enters a residence after the death of the owner and before the heir takes possession.
- The reduction of the proceeds of a will, when the debts have not yet been satisfied; the reduction of taxes due.