The most common and most likely answer to this crossword clue is the 7 letter word EXHAUST
I've seen this crossword clue in Independent
E
X
H
A
U
S
T
More clues leading to the result EXHAUST
- Run out of Gold Street going after former husband
- Run through former play by Goethe, hard for following
- Weary old bowler, perhaps, trapping us
- Use tax reforms to tackle hydrogen emission
- Emission — tax to the limit
- Old screw shut a drain
- Car part – tyre for Ford?
- Old American in headwear in lower part of estate?
- Drain top of ulcer in Texas hospital complex
- Drain pipe?
Buddy explains!

The straight part
We know that "Drain" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case drain = exhaust.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 EXHAUST mean?
EXHAUST noun- A system consisting of the parts of an engine through which burned gases or steam are discharged; see also exhaust system.
- The steam let out of a cylinder after it has done its work there.
- The dirty air let out of a room through a register or pipe provided for the purpose.
- An exhaust pipe, especially on a motor vehicle.
- Exhaust gas.
- To draw or let out wholly; to drain off completely
- To empty by drawing or letting out the contents
- To drain; to use up or expend wholly, or until the supply comes to an end
- To tire out; to wear out; to cause to be without any energy
- To bring out or develop completely
- To discuss thoroughly or completely
- To subject to the action of various solvents in order to remove all soluble substances or extractives
- Exhausted; used up.