Second best comedian? (6)
I believe the answer is:
scream
'comedian?' is the definition.
(I've seen this before)
'second best' is the wordplay.
'second' becomes 's' (common abbreviation).
'best' becomes 'cream' (as in 'the cream of the crop').
's'+'cream'='SCREAM'
(Other definitions for scream that I've seen before include "Loud piercing cry" , "Screech" , "Caution" , "Hoot - yell in pain" , "Make a piercing sound" .)