Crossword Genius

It is heard in these brief periods (4)

Ross

I believe the answer is:

secs

'these brief periods' is the definition.
(I've seen this in another clue)

'it is heard' is the wordplay.
'it' becomes 'sex' ('it' is a common euphemism for sex).
'is heard' indicates a 'sounds like' (homophone) clue.
'sex' sounds like 'SECS'.

'in' acts as a link.

(Another definition for secs that I've seen is " a very short time".)

I've seen this clue in The Guardian.
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