Publicity for Farah? (5)
I believe the answer is:
promo
'publicity' is the definition.
(short for promotion)
'for farah?' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'farah?' becomes 'Mo' (Sir Mo Farah, British Olympian).
'pro'+'mo'='PROMO'
(Other definitions for promo that I've seen before include "21 [TRAILER]" , "Advertising film or video" , "Ad" , "for [a] little while" , "Encouragement" .)