The most common and most likely answer to this crossword clue is the 8 letter word GIGAFLOP
I've seen this crossword clue in The Times
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More clues leading to the result GIGAFLOP
- Speed measurement for some circuits showing vehicle's a failure
- Job a disaster: a measure of PC’s performance?
- Computer speed means temporary job a disappointment
- Show a failure in processing speed
- Performance a failure — a measure of speed required
- High-speed show’s a failure
- Phileas Fogg? He's gone out to figure out computing speed unit
Buddy explains!

The straight part
We know that "Speed measurement for some circuits" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case speed measurement for some circuits = gigaflop.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 GIGAFLOP mean?
GIGAFLOP noun- A unit of measure for the calculating speed of a computer equal to one billion (109) floating point operations per second.