Fleeting moment (3)
(Other definitions for sec that I've seen before include "Moderately dry, champagne say" , "very short space of time" , "Religious group." , "Twinkling" , "Dry wine perhaps" .)
'fleeting moment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for trice that I've seen before include "Next to no time" , "Second" , "Very brief moment" , "Short time" , "Old use for three times" .)