To be paid nothing to fly (5)
I believe the answer is:
owing
'to be paid' is the definition.
(eg an unpaid bill is owing)
'nothing to fly' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'to fly' becomes 'wing' (synonyms).
'o'+'wing'='OWING'
(Other definitions for owing that I've seen before include "Due to, like debt" , "Unpaid" , "Outstanding as a debt" , "Still outstanding" , "(Of money) outstanding" .)