Expert with brief moment for publicity material (5)
I believe the answer is:
promo
'publicity material' is the definition.
(promotional item)
'expert with brief moment' is the wordplay.
'expert' becomes 'pro' (short for professional).
'with' is a charade indicator (letters next to each other).
'brief moment' becomes 'mo' (as in 'just a mo'; 'brief' suggests an abbreviation).
'pro'+'mo'='PROMO'
'for' acts as a link.
(Other definitions for promo that I've seen before include "Publicity for project or product (abbr)" , "for [a] little while" , "Advertising film or video" , "Encouragement" , "advertisement" .)