Flair shown by almost everyone appearing in marquee (6)
I believe the answer is:
talent
'flair' is the definition.
(I've seen this before)
'almost everyone appearing in marquee' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'everyone' becomes 'all' (I've seen this before).
'appearing in' indicates putting letters inside.
'marquee' becomes 'tent' (I've seen this before).
'all' with its last letter taken away is 'al'.
'al' inserted into 'tent' is 'TALENT'.
'shown by' is the link.
(Other definitions for talent that I've seen before include "Gift, flair" , "Special ability, may be natural" , "some scouts are looking for" , "Special gift" , "Biblical coin" .)