Presumably easy, raid becoming complicated (1,4,3)
I believe the answer is:
i dare say
'presumably' is the definition.
('I dare say' means 'presumably' or 'I expect')
'easy raid becoming complicated' is the wordplay.
'becoming complicated' indicates an anagram.
'easy'+'raid'='easyraid'
'easyraid' with letters rearranged gives 'I DARE SAY'.
(Other definitions for i dare say that I've seen before include "One would think" , "It is probable" , "It wouldn't surprise me" , "one might suppose" , "Probably" .)