What mum does, receiving letters about the future for Bill? (3,2,10)
I believe the answer is:
act of parliament
'future for bill?' is the definition.
(a parliamentary bill might become an act of law)
'what mum does receiving letters about the' is the wordplay.
I cannot quite understand how this works, but
'about' could be 'of' and 'of' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
This explanation may well be incorrect...
(Other definitions for act of parliament that I've seen before include "Bill approved" , "Law" , "Statute" .)