Unimportant person present after thirty seconds (6)
I believe the answer is:
minnow
'unimportant person' is the definition.
(minnow can figuratively mean an unimportant person)
'present after thirty seconds' is the wordplay.
'present' becomes 'now' (both can mean the current period).
'after' means one lot of letters go next to another.
'thirty seconds' becomes 'min' (half of the word 'minute').
'now' after 'min' is 'MINNOW'.
(Other definitions for minnow that I've seen before include "Very small freshwater fish of the carp family" , "Not much of a catch?" , "Very little fish" , "Little person" , "Fish; underdog" .)