The most common and most likely answer to this crossword clue is the 7 letter word INVERTS
I've seen this crossword clue in The Guardian
I
N
V
E
R
T
S
Buddy explains!
The straight part
We know that "Keels over" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case keels over = inverts.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 INVERTS mean?
INVERTS noun- A homosexual.
- An inverted arch (as in a sewer). *
- The base of a tunnel on which the road or railway may be laid and used when construction is through unstable ground. It may be flat or form a continuous curve with the tunnel arch.
- The lowest point inside a pipe at a certain point.
- An elevation of a pipe at a certain point along the pipe.
- A skateboarding trick where the skater grabs the board and plants a hand on the coping so as to balance upside-down on the lip of a ramp.
- Invertebrate
- To turn (something) upside down or inside out; to place in a contrary order or direction.
- To move (the root note of a chord) up or down an octave, resulting in a change in pitch.
- To undergo inversion, as sugar.
- To divert; to convert to a wrong use.
- To turn (the foot) inwards.