Material raised seconds after departure (6)
I believe the answer is:
egress
'departure' is the definition.
(I've seen this in another clue)
'material raised seconds' is the wordplay.
'material' becomes 'serge' (type of fabric).
'raised' is a reversal indicator (going up in a down clue).
'seconds' becomes 's' (abbreviation).
'serge' reversed gives 'egres'.
'egres'+'s'='EGRESS'
'after' is the link.
(Other definitions for egress that I've seen before include "Way out; going out" , "Departure - exit" , "Issue" , "At the right moment" , "Escape route" .)