Allow mother to have a turn first, being cooperative (8)
I believe the answer is:
amenable
'cooperative' is the definition.
(I've seen this in another clue)
'allow mother to have a turn first' is the wordplay.
'allow' becomes 'enable' (I've seen this before).
'mother' becomes 'ma' (Ma is another word for mother or mum).
'to have a turn' says the letters should be written backwards.
'first' is a charade indicator (letters next to each other).
'ma' back-to-front is 'am'.
'enable' put after 'am' is 'AMENABLE'.
'being' acts as a link.
(Other definitions for amenable that I've seen before include "Pliant" , "Willing to comply" , "Open to suggestions" , "likely to cooperate - with 3a" , "Acquiescent" .)