Speed of pigs eating paper at first seems surprising (9)
I believe the answer is:
swiftness
'speed' is the definition.
(synonyms)
'pigs eating paper at first seems surprising' is the wordplay.
'pigs' becomes 'swine' (I've seen this in another clue).
'eating' means one lot of letters goes inside another.
'paper' becomes 'FT' (the Financial Times newspaper).
'at first' says to take the initial letters.
The initial letters of 'seems surprising' is 'ss'.
'swine' going around 'ft' is 'swiftne'.
'swiftne'+'ss'='SWIFTNESS'
'of' acts as a link.
(Other definitions for swiftness that I've seen before include "speed" , "Rapidity - as of fast bird?" .)