Perhaps Mum accepts post coming up for debating group (10)
I believe the answer is:
parliament
'debating group' is the definition.
I can't judge whether this definition defines the answer.
'perhaps mum accepts post coming up' is the wordplay.
'perhaps mum' becomes 'parent' (mum is a type of parent).
'accepts' is an insertion indicator.
'post' becomes 'mail' (synonyms).
'coming up' is a reversal indicator (in a down clue, letters go up).
'mail' in reverse letter order is 'liam'.
'parent' placed around 'liam' is 'PARLIAMENT'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for parliament that I've seen before include "Diet" , "UK legislature" , "Legislative assembly" , "Houses" , "Legislative body" .)