Implausibly fast mover on yacht at sea (7)

I believe the answer is:

tachyon

'implausibly fast mover' is the definition.
(hypothetical faster-than-light particle)

'on yacht at sea' is the wordplay.
'at sea' indicates an anagram.
'on'+'yacht'='onyacht'
'onyacht' is an anagram of 'TACHYON'.

(Another definition for tachyon that I've seen is " One moving faster than light".)

I've seen this clue in The Times.

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