Everyone present and alert (3,5)
I believe the answer is:
all there
This clue is a double definition.
'everyone present' is the first definition.
(I've seen this before)
'alert' is the second definition.
(I've seen this before)
'and' acts as a link.
(Other definitions for all there that I've seen before include "with marbles?" , "Having one's wits about one (informal)" , "Total number of people attending" , "Everybody attending the event" , "right in the head" .)