Brief time in fashion, a nose condom (10)
I believe the answer is:
nanosecond
'brief time' is the definition.
(I have seen 'short time' mean 'nanosecond' so perhaps 'time' could also mean 'nanosecond'; 'brief' suggests an abbreviation)
'in fashion a nose condom' is the wordplay.
'in' indicates the answer is hidden within the clue.
'NANOSECOND' is hidden within 'fashion a nose condom'.
(Other definitions for nanosecond that I've seen before include "A very short interval of time" , "instant?" , "Tiny duration" , "Only a little flash" , "trice" .)