The best source of comedy, on paper (5)
I believe the answer is:
cream
'the best' is the definition.
(as in 'the cream of the crop')
'source of comedy on paper' is the wordplay.
'source of' says to take the initial letters.
'on' means one lot of letters go next to another.
'paper' becomes 'ream' (I've seen this before).
The first letter of 'comedy' is 'c'.
'c'+'ream'='CREAM'
(Other definitions for cream that I've seen before include "Very best; pale yellow" , "Elite; off-white" , "best people" , "Pick - fatty part of milk" , "Milk product" .)