Having lost the lead for a short time (6)
I believe the answer is:
second
'short time' is the definition.
(second is a kind of short time)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for second that I've seen before include "Short period of time" , "Runner-up; short time" , "Instant - support" , "taking silver back" , "Moment in time" .)