Expert with brief moment to create publicity (5)
I believe the answer is:
promo
'publicity' is the definition.
(short for promotion)
'expert with brief moment' is the wordplay.
'expert' becomes 'pro' (short for professional).
'with' says to put letters next to each other.
'brief moment' becomes 'mo' (as in 'just a mo'; 'brief' asks for a short form).
'pro'+'mo'='PROMO'
'to create' acts as a link.
(Other definitions for promo that I've seen before include "Encouragement" , "Ad" , "21 [TRAILER]" , "advertisement" , "Advertising film or video" .)