Due for payment, mother? True, unfortunately (6)
I believe the answer is:
mature
'due for payment' is the definition.
(eg an insurance policy might be mature)
'mother? true unfortunately' is the wordplay.
'mother?' becomes 'ma' (Ma is another word for mother or mum).
'unfortunately' indicates an anagram (a bad or unfortunate spelling).
'true' anagrammed gives 'ture'.
'ma'+'ture'='MATURE'
(Other definitions for mature that I've seen before include "Fully developed physically" , "of older years" , "Age" , "reach the end of term" , "Victor, old player" .)