Unusual foresight is a bonus not to be questioned (4,5)
I believe the answer is:
gift horse
'a bonus not to be questioned' is the definition.
(as in 'don't look a gift horse in the mouth')
'unusual foresight' is the wordplay.
'unusual' indicates anagramming the letters.
'foresight' anagrammed gives 'GIFT HORSE'.
'is' acts as a link.
(Other definitions for gift horse that I've seen before include "Chance benefit (oral exam not recommended!)" , "Hack, perhaps, given" , "Arab offered" , "'Never look a . . . . . . . . . in the mouth'" , "Don't look one in the mouth" .)