Novel, alas, unfolded unexpectedly (3,2,1,6)
I believe the answer is:
all of a sudden
'unexpectedly' is the definition.
(I've seen this before)
'novel alas unfolded' is the wordplay.
'novel' is an anagram indicator.
'alas'+'unfolded'='alasunfolded'
'alasunfolded' with letters rearranged gives 'ALL OF A SUDDEN'.
(Other definitions for all of a sudden that I've seen before include "In an unexpected manner" , "Without warning" , "Quickly and unexpectedly" , "abruptly" .)