Yell for second best (6)
I believe the answer is:
scream
'yell' is the definition.
(I know that yell can be written as scream)
'second best' is the wordplay.
'second' becomes 's' (common abbreviation).
'best' becomes 'cream' (as in 'the cream of the crop').
's'+'cream'='SCREAM'
'for' is the link.
(Other definitions for scream that I've seen before include "Make a piercing sound" , "Utter a piercing cry" , "Make high shrill sound as from fear" , "express horror" , "Loud piercing cry" .)