Due to a duck having to fly (5)
I believe the answer is:
owing
'due to' is the definition.
(I've seen this before)
'a duck having to fly' is the wordplay.
'a duck' becomes 'o' (resembles zero - 'duck' in cricket).
'having' means one lot of letters go next to another.
'to fly' becomes 'wing' (synonyms).
'o'+'wing'='OWING'
(Other definitions for owing that I've seen before include "Unsettled; on account" , "Unpaid" , "This debt has yet to be paid" , "Undischarged" , "Still outstanding" .)