Quite possibly raised abroad, a leader of yours (1,4,3)
I believe the answer is:
i dare say
'quite possibly' is the definition.
(I've seen this before)
'raised abroad a leader of yours' is the wordplay.
'abroad' indicates an anagram.
'leader of' says to take the initial letters.
The initial letter of 'yours' is 'y'.
'raised' anagrammed gives 'idares'.
'idares'+'a'+'y'='I DARE SAY'
(Other definitions for i dare say that I've seen before include "One assumes" , "Probably" , "Maybe" , "It's very likely!" , "one might suppose" .)